SQL PRIMARY KEY

SQL PRIMARY KEY

The PRIMARY KEY constraint uniquely identifies each record in a database table.
Primary keys must contain unique values.
A primary key column cannot contain NULL values.

SQL Server / Oracle / MS Access:

CREATE TABLE Persons
(
P_Id int NOT NULL PRIMARY KEY,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Address varchar(255),
City varchar(255)
)

MySQL / SQL Server / Oracle / MS Access:

CREATE TABLE Persons
(
P_Id int NOT NULL,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Address varchar(255),
City varchar(255),
CONSTRAINT pk_PersonID PRIMARY KEY (P_Id,LastName)
)

SQL PRIMARY KEY Constraint on ALTER TABLE

To create a PRIMARY KEY constraint on the "P_Id" column when the table is already created, use the following SQL:
MySQL / SQL Server / Oracle / MS Access:

ALTER TABLE Persons
ADD PRIMARY KEY (P_Id)
To allow naming of a PRIMARY KEY constraint, and for defining a PRIMARY KEY constraint on multiple columns, use the following SQL syntax:
MySQL / SQL Server / Oracle / MS Access:

ALTER TABLE Persons
ADD CONSTRAINT pk_PersonID PRIMARY KEY (P_Id,LastName)

Note: If you use the ALTER TABLE statement to add a primary key, the primary key column(s) must already have been declared to not contain NULL values (when the table was first created).

To DROP a PRIMARY KEY Constraint

To drop a PRIMARY KEY constraint, use the following SQL:
ALTER TABLE Persons
DROP CONSTRAINT pk_PersonID


To see the Constraint of table use <> in sql server

SQL FOREIGN KEY

SQL FOREIGN KEY

A FOREIGN KEY in one table points to a PRIMARY KEY in another table.
The "Persons" table:
P_Id LastName FirstName Address City
1 Hansen Ola Timoteivn 10 Sandnes
2 Svendson Tove Borgvn 23 Sandnes
3 Pettersen Kari Storgt 20 Stavanger
The "Orders" table:
O_Id OrderNo P_Id
1 77895 3
2 44678 3
3 22456 2
4 24562 1

Note that the "P_Id" column in the "Orders" table points to the "P_Id" column in the "Persons" table.
The "P_Id" column in the "Persons" table is the PRIMARY KEY in the "Persons" table.
The "P_Id" column in the "Orders" table is a FOREIGN KEY in the "Orders" table.
The FOREIGN KEY constraint is used to prevent actions that would destroy links between tables.

SQL Server / Oracle / MS Access:

CREATE TABLE Orders
(
O_Id int NOT NULL PRIMARY KEY,
OrderNo int NOT NULL,
P_Id int FOREIGN KEY REFERENCES Persons(P_Id)
)

MySQL / SQL Server / Oracle / MS Access:

CREATE TABLE Orders
(
O_Id int NOT NULL,
OrderNo int NOT NULL,
P_Id int,
PRIMARY KEY (O_Id),
CONSTRAINT fk_PerOrders FOREIGN KEY (P_Id)
REFERENCES Persons(P_Id)
)


To DROP a FOREIGN KEY Constraint

SQL Server / Oracle / MS Access:

ALTER TABLE Orders
DROP CONSTRAINT fk_PerOrders

SQL PRIMARY KEY
The PRIMARY KEY constraint uniquely identifies each record in a database table.
Primary keys must contain unique values.

A primary key column cannot contain NULL values.
SQL Server / Oracle / MS Access:
CREATE TABLE Persons
(
P_Id int NOT NULL PRIMARY KEY,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Address varchar(255),
City varchar(255)
)

MySQL / SQL Server / Oracle / MS Access:

CREATE TABLE Persons
(
P_Id int NOT NULL,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Address varchar(255),
City varchar(255),
CONSTRAINT pk_PersonID PRIMARY KEY (P_Id,LastName)
)

Meaning For Dotnet First line of Code

Meaning For Dotnet First line of Code

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>
@ Page directive on top of page
Page Language="C#" Denotes C# language is used in this project

AutoEventWireup attribute defaults to true,

ASP.NET does not require that you explicitly bind event handlers to a page event such as Load.

When AutoEventWireup is false, you must explicitly bind the event to a method. For example, if you have a Page_Load method in the code for a page, the method will be called in response to the Load event only if you write code like that in the following example

Otherwise you have to bind the event explicitly

public partial class AutoEventWireupExample : System.Web.UI.Page
{
protected void Page_Load(object sender, System.EventArgs e)
{
Response.Write("Executing Page_Load");
}
override protected void OnInit(EventArgs e)
{
this.Load += new System.EventHandler(this.Page_Load);
}
}

The following code example shows how to set or read the AutoEventWireup property in code.
// Get the current AutoEventWireup property value.
Console.WriteLine(
"Current AutoEventWireup value: '{0}'",
pagesSection.AutoEventWireup);

// Set the AutoEventWireup property to false.
pagesSection.AutoEventWireup = false;


The following example shows the two forms of method signatures that are automatically attached to page events when AutoEventWireup is true.

protected void Page_Load(object sender, EventArgs e)
{
Response.Write("Hello world");

}
// This method will be automatically bound to the Load event
// when AutoEventWireup is true only if no overload having
// object and EventArgs parameters is found.
protected void Page_Load()
{
Response.Write("Hello world");
}



// Following are three alternative ways of binding an event
// handler to an event when AutoEventWireup is false. For
// any given event do this binding only once or the handler
// will be called multiple times.

// You can wire up events in the page's constructor.
public _Default()
{
Load += new EventHandler(Page_Load);
}

// You can override the OnInit event and wire up events there.
protected override void OnInit(EventArgs e)
{
base.OnInit(e);
Load += new EventHandler(Page_Load);
}

// Or you can override the event's OnEventname method and
// call your handler from there. You can also put the code
// execute when the event fires within the override method itself.
protected override void OnLoad(EventArgs e)
{
Page_Load(null, null);
base.OnLoad(e);
}

protected void Page_Load(object sender, EventArgs e)
{
Response.Write("Hello world");
}

Inherits="_Default"

the Inherits attribute tells the runtime the name of the class it will use as a base class for this web form,

look at the CodeFile (code-behind) file for the ASPX page.

using System;
using System.Web.UI;

public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{

}
}
‘partial’ keyword.
Partial allows us to split a class definition across two or more source code files.
The partial keyword plays an important role because it will allow the runtime to extend the definition of our _Default class with additional members.

Difference between Stored procedure vs User Functions in Sql server

Difference between Stored procedure vs User Functions in Sql server

• Procedure may return none or more values. Function must always return one value either a scalar value or a table.

• A user-defined function takes zero or more input parameters and returns either a scalar value or a table.

• Procedure have input,output parameters.Functions have only input parameters.

• Stored procedures are called independently by EXEC command whereas Functions are called from within SQL statement.


• Functions can be called from procedure. Procedures cannot be called from function.


• Exception can be handled in Procedure by try-catch block but try-catch block cannot be used in a function.(error-handling)


• Transaction management possible in procedure but not in function.

Difference Between SCOPE_IDENTITY and ROWCOUNT in sql server

Difference Between SCOPE_IDENTITY and atatROWCOUNT in sql server

SCOPE_IDENTITY

Returns the last identity value inserted into an identity column in the same scope. A scope is a module: a stored procedure, trigger, function, or batch. Therefore, two statements are in the same scope if they are in the same stored procedure, function, or batch.

ROWCOUNT"

Returns the number of rows affected by the last statement.

How to convert from string to date / datetime? in sql server

Execute the following T-SQL scripts in Microsoft SQL Server Manangement Studio Query Editor to demonstrate T-SQL convert and cast functions in transforming string date, string time & string datetime data to datetime data type. T-SQL date / datetime functions usage examples are presented as well.

-- SQL Server string to date / datetime conversion - datetime string format sql server

-- MSSQL string to datetime conversion - convert char to date - convert varchar to date

-- Subtract 100 from style number (format) for yy instead yyyy (or ccyy with century)

SELECT convert(datetime, 'Oct 23 2012 11:01AM', 100) -- mon dd yyyy hh:mmAM (or PM)

SELECT convert(datetime, 'Oct 23 2012 11:01AM') -- 2012-10-23 11:01:00.000



-- Without century (yy) string date conversion - convert string to datetime function

SELECT convert(datetime, 'Oct 23 12 11:01AM', 0) -- mon dd yy hh:mmAM (or PM)

SELECT convert(datetime, 'Oct 23 12 11:01AM') -- 2012-10-23 11:01:00.000



-- Convert string to datetime sql - convert string to date sql - sql dates format

-- T-SQL convert string to datetime - SQL Server convert string to date

SELECT convert(datetime, '10/23/2016', 101) -- mm/dd/yyyy

SELECT convert(datetime, '2016.10.23', 102) -- yyyy.mm.dd

SELECT convert(datetime, '23/10/2016', 103) -- dd/mm/yyyy

SELECT convert(datetime, '23.10.2016', 104) -- dd.mm.yyyy

SELECT convert(datetime, '23-10-2016', 105) -- dd-mm-yyyy

-- mon types are nondeterministic conversions, dependent on language setting

SELECT convert(datetime, '23 OCT 2016', 106) -- dd mon yyyy

SELECT convert(datetime, 'Oct 23, 2016', 107) -- mon dd, yyyy

-- 2016-10-23 00:00:00.000

SELECT convert(datetime, '20:10:44', 108) -- hh:mm:ss

-- 1900-01-01 20:10:44.000



-- mon dd yyyy hh:mm:ss:mmmAM (or PM) - sql time format - SQL Server datetime format

SELECT convert(datetime, 'Oct 23 2016 11:02:44:013AM', 109)

-- 2016-10-23 11:02:44.013

SELECT convert(datetime, '10-23-2016', 110) -- mm-dd-yyyy

SELECT convert(datetime, '2016/10/23', 111) -- yyyy/mm/dd

-- YYYYMMDD ISO date format works at any language setting - international standard

SELECT convert(datetime, '20161023')

SELECT convert(datetime, '20161023', 112) -- yyyymmdd

-- 2016-10-23 00:00:00.000

SELECT convert(datetime, '23 Oct 2016 11:02:07:577', 113) -- dd mon yyyy hh:mm:ss:mmm

-- 2016-10-23 11:02:07.577

SELECT convert(datetime, '20:10:25:300', 114) -- hh:mm:ss:mmm(24h)

-- 1900-01-01 20:10:25.300

SELECT convert(datetime, '2016-10-23 20:44:11', 120) -- yyyy-mm-dd hh:mm:ss(24h)

-- 2016-10-23 20:44:11.000

SELECT convert(datetime, '2016-10-23 20:44:11.500', 121) -- yyyy-mm-dd hh:mm:ss.mmm

-- 2016-10-23 20:44:11.500


-- Style 126 is ISO 8601 format: international standard - works with any language setting

SELECT convert(datetime, '2008-10-23T18:52:47.513', 126) -- yyyy-mm-ddThh:mm:ss(.mmm)

-- 2008-10-23 18:52:47.513


-- Convert DDMMYYYY format to datetime - sql server to date / datetime

SELECT convert(datetime, STUFF(STUFF('31012016',3,0,'-'),6,0,'-'), 105)

-- 2016-01-31 00:00:00.000

-- SQL Server T-SQL string to datetime conversion without century - some exceptions
-- nondeterministic means language setting dependent such as Mar/Mär/mars/márc

SELECT convert(datetime, 'Oct 23 16 11:02:44AM') -- Default

SELECT convert(datetime, '10/23/16', 1) -- mm/dd/yy U.S.

SELECT convert(datetime, '16.10.23', 2) -- yy.mm.dd ANSI

SELECT convert(datetime, '23/10/16', 3) -- dd/mm/yy UK/FR

SELECT convert(datetime, '23.10.16', 4) -- dd.mm.yy German

SELECT convert(datetime, '23-10-16', 5) -- dd-mm-yy Italian

SELECT convert(datetime, '23 OCT 16', 6) -- dd mon yy non-det.

SELECT convert(datetime, 'Oct 23, 16', 7) -- mon dd, yy non-det.

SELECT convert(datetime, '20:10:44', 8) -- hh:mm:ss

SELECT convert(datetime, 'Oct 23 16 11:02:44:013AM', 9) -- Default with msec

SELECT convert(datetime, '10-23-16', 10) -- mm-dd-yy U.S.

SELECT convert(datetime, '16/10/23', 11) -- yy/mm/dd Japan

SELECT convert(datetime, '161023', 12) -- yymmdd ISO

SELECT convert(datetime, '23 Oct 16 11:02:07:577', 13) -- dd mon yy hh:mm:ss:mmm EU dflt

SELECT convert(datetime, '20:10:25:300', 14) -- hh:mm:ss:mmm(24h)

SELECT convert(datetime, '2016-10-23 20:44:11',20) -- yyyy-mm-dd hh:mm:ss(24h) ODBC can.

SELECT convert(datetime, '2016-10-23 20:44:11.500', 21)-- yyyy-mm-dd hh:mm:ss.mmm ODBC

------------



-- SQL Datetime Data Type: Combine date & time string into datetime - sql hh mm ss

-- String to datetime - mssql datetime - sql convert date - sql concatenate string

DECLARE @DateTimeValue varchar(32), @DateValue char(8), @TimeValue char(6)



SELECT @DateValue = '20120718',

@TimeValue = '211920'

SELECT @DateTimeValue =

convert(varchar, convert(datetime, @DateValue), 111)

+ ' ' + substring(@TimeValue, 1, 2)

+ ':' + substring(@TimeValue, 3, 2)

+ ':' + substring(@TimeValue, 5, 2)

SELECT

DateInput = @DateValue, TimeInput = @TimeValue,

DateTimeOutput = @DateTimeValue;

/*

DateInput TimeInput DateTimeOutput

20120718 211920 2012/07/18 21:19:20

*/


/* Datetime 8 bytes internal storage structure
o 1st 4 bytes: number of days after the base date 1900-01-01

o 2nd 4 bytes: number of milliseconds since midnight */

-- SQL convert seconds to HH:MM:SS - sql times format - sql hh mm

DECLARE @Seconds INT

SET @Seconds = 20000

SELECT HH = @Seconds / 3600, MM = (@Seconds%3600) / 60, SS = (@Seconds%60)

/* HH MM SS

5 33 20 */
------------



-- SQL Server 2008 convert datetime to date - sql yyyy mm dd

SELECT TOP (3) OrderDate = CONVERT(date, OrderDate),

Today = CONVERT(date, getdate())

FROM AdventureWorks2008.Sales.SalesOrderHeader

ORDER BY newid();

/* OrderDate Today

2003-07-09 2012-06-18

2003-09-26 2012-06-18

2004-02-15 2012-06-18 */

------------

-- SQL date yyyy mm dd - sqlserver yyyy mm dd - date format yyyymmdd

SELECT CONVERT(VARCHAR(10), GETDATE(), 111) AS [YYYY/MM/DD]

/* YYYY/MM/DD

2015/07/11 */

SELECT CONVERT(VARCHAR(10), GETDATE(), 112) AS [YYYYMMDD]

/* YYYYMMDD

20150711 */

SELECT REPLACE(CONVERT(VARCHAR(10), GETDATE(), 111),'/',' ') AS [YYYY MM DD]

/* YYYY MM DD

2015 07 11 */
-- Converting to special (non-standard) date fomats: DD-MMM-YY
SELECT UPPER(REPLACE(CONVERT(VARCHAR,GETDATE(),6),' ','-'))
-- 07-MAR-14
------------

-- SQL convert date string to datetime - time set to 00:00:00.000 or 12:00AM

PRINT CONVERT(datetime,'07-10-2012',110) -- Jul 10 2012 12:00AM

PRINT CONVERT(datetime,'2012/07/10',111) -- Jul 10 2012 12:00AM

PRINT CONVERT(datetime,'20120710', 112) -- Jul 10 2012 12:00AM

------------



-- String to date conversion - sql date yyyy mm dd - sql date formatting

-- SQL Server cast string to date - sql convert date to datetime

SELECT [Date] = CAST (@DateValue AS datetime)

-- 2012-07-18 00:00:00.000



-- SQL convert string date to different style - sql date string formatting

SELECT CONVERT(varchar, CONVERT(datetime, '20140508'), 100)

-- May 8 2014 12:00AM

-- SQL Server convert date to integer

DECLARE @Date datetime; SET @Date = getdate();

SELECT DateAsInteger = CAST (CONVERT(varchar,@Date,112) as INT);

-- Result: 20161225



-- SQL Server convert integer to datetime

DECLARE @iDate int

SET @iDate = 20151225

SELECT IntegerToDatetime = CAST(convert(varchar,@iDate) as datetime)

-- 2015-12-25 00:00:00.000



-- Alternates: date-only datetime values

-- SQL Server floor date - sql convert datetime

SELECT [DATE-ONLY]=CONVERT(DATETIME, FLOOR(CONVERT(FLOAT, GETDATE())))

SELECT [DATE-ONLY]=CONVERT(DATETIME, FLOOR(CONVERT(MONEY, GETDATE())))

-- SQL Server cast string to datetime

-- SQL Server datetime to string convert

SELECT [DATE-ONLY]=CAST(CONVERT(varchar, GETDATE(), 101) AS DATETIME)

-- SQL Server dateadd function - T-SQL datediff function

-- SQL strip time from date - MSSQL strip time from datetime

SELECT getdate() ,DATEADD(dd, DATEDIFF(dd, 0, getdate()), 0)

-- Results: 2016-01-23 05:35:52.793 2016-01-23 00:00:00.000

-- String date - 10 bytes of storage

SELECT [STRING DATE]=CONVERT(varchar, GETDATE(), 110)

SELECT [STRING DATE]=CONVERT(varchar, CURRENT_TIMESTAMP, 110)

-- Same results: 01-02-2012



-- SQL Server cast datetime as string - sql datetime formatting

SELECT stringDateTime=CAST (getdate() as varchar) -- Dec 29 2012 3:47AM


----------

-- SQL date range BETWEEN operator

----------

-- SQL date range select - date range search - T-SQL date range query - sql date ranges

-- Count Sales Orders for 2003 OCT-NOV

DECLARE @StartDate DATETIME, @EndDate DATETIME

SET @StartDate = convert(DATETIME,'10/01/2003',101)

SET @EndDate = convert(DATETIME,'11/30/2003',101)



SELECT @StartDate, @EndDate

-- 2003-10-01 00:00:00.000 2003-11-30 00:00:00.000

SELECT DATEADD(DAY,1,@EndDate),

DATEADD(ms,-3,DATEADD(DAY,1,@EndDate))

-- 2003-12-01 00:00:00.000 2003-11-30 23:59:59.997



-- MSSQL date range select using >= and <

SELECT [Sales Orders for 2003 OCT-NOV] = COUNT(* )

FROM Sales.SalesOrderHeader

WHERE OrderDate >= @StartDate AND OrderDate < DATEADD(DAY,1,@EndDate)

/* Sales Orders for 2003 OCT-NOV

3668 */



-- Equivalent date range query using BETWEEN comparison

-- It requires a bit of trick programming

SELECT [Sales Orders for 2003 OCT-NOV] = COUNT(* )

FROM Sales.SalesOrderHeader

WHERE OrderDate BETWEEN @StartDate AND DATEADD(ms,-3,DATEADD(DAY,1,@EndDate))

-- 3668



USE AdventureWorks;

-- SQL between string dates

SELECT POs=COUNT(*) FROM Purchasing.PurchaseOrderHeader

WHERE OrderDate BETWEEN '20040201' AND '20040210' -- Result: 108



-- SQL BETWEEN dates without time - time stripped - time removed - date part only

SELECT POs=COUNT(*) FROM Purchasing.PurchaseOrderHeader

WHERE DATEDIFF(dd,0,OrderDate)

BETWEEN DATEDIFF(dd,0,'20040201 12:11:39') AND DATEDIFF(dd,0,'20040210 14:33:19')

-- 108

-- BETWEEN is equivalent to >=...AND....<=

SELECT POs=COUNT(*) FROM Purchasing.PurchaseOrderHeader

WHERE OrderDate

BETWEEN '2004-02-01 00:00:00.000' AND '2004-02-10 00:00:00.000'

/* Orders with OrderDates

'2004-02-10 00:00:01.000' - 1 second after midnight (12:00AM)

'2004-02-10 00:01:00.000' - 1 minute after midnight

'2004-02-10 01:00:00.000' - 1 hour after midnight

are not included in the two queries above. */

-- To include the entire day of 2004-02-10 use:

SELECT POs=COUNT(*) FROM Purchasing.PurchaseOrderHeader

WHERE OrderDate >= '20040201' AND OrderDate < '20040211'

----------

-- Date validation function ISDATE - returns 1 or 0 - SQL datetime functions

------------

DECLARE @StringDate varchar(32)

SET @StringDate = '2011-03-15 18:50'

IF EXISTS( SELECT * WHERE ISDATE(@StringDate) = 1)

PRINT 'VALID DATE: ' + @StringDate

ELSE

PRINT 'INVALID DATE: ' + @StringDate

GO

-- Result: VALID DATE: 2011-03-15 18:50



DECLARE @StringDate varchar(32)

SET @StringDate = '20112-03-15 18:50'

IF EXISTS( SELECT * WHERE ISDATE(@StringDate) = 1)

PRINT 'VALID DATE: ' + @StringDate

ELSE

PRINT 'INVALID DATE: ' + @StringDate

GO

-- Result: INVALID DATE: 20112-03-15 18:50

-- First and last day of date periods - SQL Server 2008 and on code

DECLARE @Date DATE = '20161023'

SELECT ReferenceDate = @Date

SELECT FirstDayOfYear = CONVERT(DATE, DATEADD(yy, DATEDIFF(yy,0, @Date),0))

SELECT LastDayOfYear = CONVERT(DATE, DATEADD(yy, DATEDIFF(yy,0, @Date)+1,-1))

SELECT FirstDayOfSemester = CONVERT(DATE, DATEADD(qq,((DATEDIFF(qq,0,@Date)/2)*2),0))

SELECT LastDayOfSemester = CONVERT(DATE, DATEADD(qq,((DATEDIFF(qq,0,@Date)/2)*2)+2,-1))

SELECT FirstDayOfQuarter = CONVERT(DATE, DATEADD(qq, DATEDIFF(qq,0, @Date),0))

-- 2016-10-01

SELECT LastDayOfQuarter = CONVERT(DATE, DATEADD(qq, DATEDIFF(qq,0, @Date)+1,-1))

-- 2016-12-31

SELECT FirstDayOfMonth = CONVERT(DATE, DATEADD(mm, DATEDIFF(mm,0, @Date),0))

SELECT LastDayOfMonth = CONVERT(DATE, DATEADD(mm, DATEDIFF(mm,0, @Date)+1,-1))

SELECT FirstDayOfWeek = CONVERT(DATE, DATEADD(wk, DATEDIFF(wk,0, @Date),0))

SELECT LastDayOfWeek = CONVERT(DATE, DATEADD(wk, DATEDIFF(wk,0, @Date)+1,-1))

-- 2016-10-30



------------

-- Selected named date styles
------------

DECLARE @DateTimeValue varchar(32)

-- US-Style

SELECT @DateTimeValue = '10/23/2016'

SELECT StringDate=@DateTimeValue,

[US-Style] = CONVERT(datetime, @DatetimeValue)



SELECT @DateTimeValue = '10/23/2016 23:01:05'

SELECT StringDate = @DateTimeValue,

[US-Style] = CONVERT(datetime, @DatetimeValue)



-- UK-Style, British/French - convert string to datetime sql

-- sql convert string to datetime

SELECT @DateTimeValue = '23/10/16 23:01:05'

SELECT StringDate = @DateTimeValue,

[UK-Style] = CONVERT(datetime, @DatetimeValue, 3)



SELECT @DateTimeValue = '23/10/2016 04:01 PM'

SELECT StringDate = @DateTimeValue,

[UK-Style] = CONVERT(datetime, @DatetimeValue, 103)



-- German-Style

SELECT @DateTimeValue = '23.10.16 23:01:05'

SELECT StringDate = @DateTimeValue,

[German-Style] = CONVERT(datetime, @DatetimeValue, 4)



SELECT @DateTimeValue = '23.10.2016 04:01 PM'

SELECT StringDate = @DateTimeValue,

[German-Style] = CONVERT(datetime, @DatetimeValue, 104)

------------



-- Double conversion to US-Style 107 with century: Oct 23, 2016

SET @DateTimeValue='10/23/16'

SELECT StringDate=@DateTimeValue,

[US-Style] = CONVERT(varchar, CONVERT(datetime, @DateTimeValue),107)



-- Using DATEFORMAT - UK-Style - SQL dateformat

SET @DateTimeValue='23/10/16'

SET DATEFORMAT dmy

SELECT StringDate=@DateTimeValue,

[Date Time] = CONVERT(datetime, @DatetimeValue)

-- Using DATEFORMAT - US-Style

SET DATEFORMAT mdy

-- Convert date string from DD/MM/YYYY UK format to MM/DD/YYYY US format
DECLARE @UKdate char(10) = '15/03/2016'
SELECT CONVERT(CHAR(10), CONVERT(datetime, @UKdate,103),101)

-- 03/15/2016

-- DATEPART datetime function example - SQL Server datetime functions

SELECT * FROM Northwind.dbo.Orders

WHERE DATEPART(YEAR, OrderDate) = '1996' AND

DATEPART(MONTH,OrderDate) = '07' AND

DATEPART(DAY, OrderDate) = '10'



-- Alternate syntax for DATEPART example

SELECT * FROM Northwind.dbo.Orders

WHERE YEAR(OrderDate) = '1996' AND

MONTH(OrderDate) = '07' AND

DAY(OrderDate) = '10'
------------

------------

-- T-SQL calculate the number of business days function / UDF - exclude SAT & SUN

------------

CREATE FUNCTION fnBusinessDays (@StartDate DATETIME, @EndDate DATETIME)

RETURNS INT AS

BEGIN

IF (@StartDate IS NULL OR @EndDate IS NULL) RETURN (0)

DECLARE @i INT = 0;

WHILE (@StartDate <= @EndDate)

BEGIN

SET @i = @i + CASE

WHEN datepart(dw,@StartDate) BETWEEN 2 AND 6 THEN 1

ELSE 0

END

SET @StartDate = @StartDate + 1

END -- while

RETURN (@i)

END -- function

GO

SELECT dbo.fnBusinessDays('2016-01-01','2016-12-31')

-- 261

------------

-- T-SQL DATENAME function usage for weekdays

SELECT DayName=DATENAME(weekday, OrderDate), SalesPerWeekDay = COUNT(*)

FROM AdventureWorks2008.Sales.SalesOrderHeader

GROUP BY DATENAME(weekday, OrderDate), DATEPART(weekday,OrderDate)

ORDER BY DATEPART(weekday,OrderDate)

/* DayName SalesPerWeekDay

Sunday 4482

Monday 4591

Tuesday 4346.... */



-- DATENAME application for months

SELECT MonthName=DATENAME(month, OrderDate), SalesPerMonth = COUNT(*)

FROM AdventureWorks2008.Sales.SalesOrderHeader

GROUP BY DATENAME(month, OrderDate), MONTH(OrderDate) ORDER BY MONTH(OrderDate)

/* MonthName SalesPerMonth

January 2483

February 2686

March 2750

April 2740.... */



-- Getting month name from month number

SELECT DATENAME(MM,DATEADD(MM,7,-1)) -- July

------------

------------

-- Extract string date from text with PATINDEX pattern matching

-- Apply sql server string to date conversion

------------

USE tempdb;

go

CREATE TABLE InsiderTransaction (

InsiderTransactionID int identity primary key,

TradeDate datetime,

TradeMsg varchar(256),

ModifiedDate datetime default (getdate()))

go



-- Populate table with dummy data

INSERT InsiderTransaction (TradeMsg) VALUES(

'INSIDER TRAN QABC Hammer, Bruce D. CSO 09-02-08 Buy 2,000 6.10')

INSERT InsiderTransaction (TradeMsg) VALUES(

'INSIDER TRAN QABC Schmidt, Steven CFO 08-25-08 Buy 2,500 6.70')

INSERT InsiderTransaction (TradeMsg) VALUES(

'INSIDER TRAN QABC Hammer, Bruce D. CSO 08-20-08 Buy 3,000 8.59')

INSERT InsiderTransaction (TradeMsg) VALUES(

'INSIDER TRAN QABC Walters, Jeff CTO 08-15-08 Sell 5,648 8.49')

INSERT InsiderTransaction (TradeMsg) VALUES(

'INSIDER TRAN QABC Walters, Jeff CTO 08-15-08 Option Execute 5,648 2.15')

INSERT InsiderTransaction (TradeMsg) VALUES(

'INSIDER TRAN QABC Hammer, Bruce D. CSO 07-31-08 Buy 5,000 8.05')

INSERT InsiderTransaction (TradeMsg) VALUES(

'INSIDER TRAN QABC Lennot, Mark B. Director 08-31-07 Buy 1,500 9.97')

INSERT InsiderTransaction (TradeMsg) VALUES(

'INSIDER TRAN QABC O''Neal, Linda COO 08-01-08 Sell 5,000 6.50')

go



-- Extract dates from stock trade message text

-- Pattern match for MM-DD-YY using the PATINDEX string function

SELECT TradeDate=substring(TradeMsg,

patindex('%[01][0-9]-[0123][0-9]-[0-9][0-9]%', TradeMsg),8)

FROM InsiderTransaction

WHERE patindex('%[01][0-9]-[0123][0-9]-[0-9][0-9]%', TradeMsg) > 0

/* Partial results

TradeDate

09-02-08

08-25-08

08-20-08 */



-- Update table with extracted date

-- Convert string date to datetime

UPDATE InsiderTransaction

SET TradeDate = convert(datetime, substring(TradeMsg,

patindex('%[01][0-9]-[0123][0-9]-[0-9][0-9]%', TradeMsg),8))

WHERE patindex('%[01][0-9]-[0123][0-9]-[0-9][0-9]%', TradeMsg) > 0



SELECT * FROM InsiderTransaction ORDER BY TradeDate desc

/* Partial results

InsiderTransactionID TradeDate TradeMsg ModifiedDate

1 2008-09-02 00:00:00.000 INSIDER TRAN QABC Hammer, Bruce D. CSO 09-02-08 Buy 2,000 6.10 2008-12-22 20:25:19.263

2 2008-08-25 00:00:00.000 INSIDER TRAN QABC Schmidt, Steven CFO 08-25-08 Buy 2,500 6.70 2008-12-22 20:25:19.263

3 2008-08-20 00:00:00.000 INSIDER TRAN QABC Hammer, Bruce D. CSO 08-20-08 Buy 3,000 8.59 2008-12-22 20:25:19.263 */

-- Cleanup task

DROP TABLE InsiderTransaction



/************



VALID DATE RANGES FOR DATE / DATETIME DATA TYPES



DATE (3 bytes) date range:

January 1, 1 A.D. through December 31, 9999 A.D.



SMALLDATETIME (4 bytes) date range:

January 1, 1900 through June 6, 2079



DATETIME (8 bytes) date range:

January 1, 1753 through December 31, 9999



DATETIME2 (6-8 bytes) date range:

January 1, 1 A.D. through December 31, 9999 A.D.



-- The statement below will give a date range error

SELECT CONVERT(smalldatetime, '2110-01-01')

/* Msg 242, Level 16, State 3, Line 1

The conversion of a varchar data type to a smalldatetime data type

resulted in an out-of-range value. */

************/

------------

-- SQL CONVERT DATE/DATETIME script applying table variable

------------

-- SQL Server convert date

-- Datetime column is converted into date only string column

DECLARE @sqlConvertDate TABLE ( DatetimeColumn datetime,

DateColumn char(10));

INSERT @sqlConvertDate (DatetimeColumn) SELECT GETDATE()



UPDATE @sqlConvertDate

SET DateColumn = CONVERT(char(10), DatetimeColumn, 111)

SELECT * FROM @sqlConvertDate



-- SQL Server convert datetime - String date column is converted into datetime column

UPDATE @sqlConvertDate

SET DatetimeColumn = CONVERT(Datetime, DateColumn, 111)

SELECT * FROM @sqlConvertDate



-- Equivalent formulation - SQL Server cast datetime

UPDATE @sqlConvertDate

SET DatetimeColumn = CAST(DateColumn AS datetime)

SELECT * FROM @sqlConvertDate

/* First results

DatetimeColumn DateColumn

2012-12-25 15:54:10.363 2012/12/25 */



/* Second results:

DatetimeColumn DateColumn

2012-12-25 00:00:00.000 2012/12/25 */

------------

-- SQL date sequence generation with DATEADD & table variable

-- SQL Server cast datetime to string - SQL Server insert default values method

DECLARE @Sequence table (Sequence int identity(1,1))

DECLARE @i int; SET @i = 0

WHILE ( @i < 500)

BEGIN

INSERT @Sequence DEFAULT VALUES

SET @i = @i + 1

END

SELECT DateSequence = CAST(DATEADD(day, Sequence,getdate()) AS varchar) FROM @Sequence

/* Partial results:

DateSequence

Dec 31 2008 3:02AM

Jan 1 2009 3:02AM

Jan 2 2009 3:02AM

Jan 3 2009 3:02AM

Jan 4 2009 3:02AM

Jan 5 2009 3:02AM */



------------

-- SQL Last Week calculations

------------

-- SQL last Friday

-- Implied string to datetime conversions in DATEADD & DATEDIFF

DECLARE @BaseFriday CHAR(8), @LastFriday datetime, @LastMonday datetime

SET @BaseFriday = '19000105'

SELECT @LastFriday = DATEADD(dd,

(DATEDIFF (dd, @BaseFriday, CURRENT_TIMESTAMP) / 7) * 7, @BaseFriday)

SELECT [Last Friday] = @LastFriday

-- Result: 2008-12-26 00:00:00.000



-- SQL last Monday (last week's Monday)

SELECT @LastMonday=DATEADD(dd,

(DATEDIFF (dd, @BaseFriday, CURRENT_TIMESTAMP) / 7) * 7 - 4, @BaseFriday)

SELECT [Last Monday]= @LastMonday

-- Result: 2008-12-22 00:00:00.000



-- SQL last week - SUN - SAT

SELECT [Last Week] = CONVERT(varchar,dateadd(day, -1, @LastMonday), 101)+ ' - ' +

CONVERT(varchar,dateadd(day, 1, @LastFriday), 101)

-- Result: 12/21/2008 - 12/27/2008



-----------------

-- Specific day calculations

------------

-- First day of current month

SELECT dateadd(month, datediff(month, 0, getdate()), 0)

-- 15th day of current month

SELECT dateadd(day,14,dateadd(month,datediff(month,0,getdate()),0))

-- First Monday of current month

SELECT dateadd(day, (9-datepart(weekday,

dateadd(month, datediff(month, 0, getdate()), 0)))%7,

dateadd(month, datediff(month, 0, getdate()), 0))

-- Last Friday of current month

SELECT dateadd(day, -7+(6-datepart(weekday,

dateadd(month, datediff(month, 0, getdate())+1, 0)))%7,

dateadd(month, datediff(month, 0, getdate())+1, 0))

-- First day of next month

SELECT dateadd(month, datediff(month, 0, getdate())+1, 0)

-- 15th of next month

SELECT dateadd(day,14, dateadd(month, datediff(month, 0, getdate())+1, 0))

-- First Monday of next month

SELECT dateadd(day, (9-datepart(weekday,

dateadd(month, datediff(month, 0, getdate())+1, 0)))%7,

dateadd(month, datediff(month, 0, getdate())+1, 0))



------------

-- SQL Last Date calculations

------------

-- Last day of prior month - Last day of previous month

SELECT convert( varchar, dateadd(dd,-1,DATEADD(mm, DATEDIFF(mm,0,getdate() ), 0)),101)

-- 01/31/2019

-- Last day of current month

SELECT convert( varchar, dateadd(dd,-1,DATEADD(mm, DATEDIFF(mm,0,getdate())+1, 0)),101)

-- 02/28/2019

-- Last day of prior quarter - Last day of previous quarter

SELECT convert( varchar, dateadd(dd,-1,DATEADD(qq, DATEDIFF(qq,0,getdate() ), 0)),101)

-- 12/31/2018

-- Last day of current quarter - Last day of current quarter

SELECT convert( varchar, dateadd(dd,-1,DATEADD(qq, DATEDIFF(qq,0,getdate())+1, 0)),101)

-- 03/31/2019

-- Last day of prior year - Last day of previous year

SELECT convert( varchar, dateadd(dd,-1,DATEADD(yy, DATEDIFF(yy,0,getdate() ), 0)),101)

-- 12/31/2018

-- Last day of current year

SELECT convert( varchar, dateadd(dd,-1,DATEADD(yy, DATEDIFF(yy,0,getdate())+1, 0)),101)

-- 12/31/2019

------------

------------

-- SQL Server dateformat and language setting

------------

-- T-SQL set language - String to date conversion

SET LANGUAGE us_english

SELECT CAST('2018-03-15' AS datetime)

-- 2018-03-15 00:00:00.000



SET LANGUAGE british

SELECT CAST('2018-03-15' AS datetime)

/* Msg 242, Level 16, State 3, Line 2

The conversion of a varchar data type to a datetime data type resulted in

an out-of-range value.

*/

SELECT CAST('2018-15-03' AS datetime)

-- 2018-03-15 00:00:00.000



SET LANGUAGE us_english



-- SQL dateformat with language dependency

SELECT name, alias, dateformat

FROM sys.syslanguages

WHERE langid in (0,1,2,4,5,6,7,10,11,13,23,31)

GO

/*

name alias dateformat

us_english English mdy

Deutsch German dmy

Français French dmy

Dansk Danish dmy

Español Spanish dmy

Italiano Italian dmy

Nederlands Dutch dmy

Suomi Finnish dmy

Svenska Swedish ymd

magyar Hungarian ymd

British British English dmy

Arabic Arabic dmy

*/

------------

To Find Highest Salary, nth Highest Salary, Lowest Salary, nth Lowest Salary

To Find Highest Salary, nth Highest Salary, Lowest Salary, nth Lowest Salary

Correlated sub queries are more generalized to find n'th highest or nth lowest salary.

To Find Maximum Salary

SELECT * FROM `student` WHERE mark=(select max(mark) from student)

n means 1 st, 2nd, 3rd highest or lowest salary dont give n values,Give n-1 values
For eg
please give

(if you want 2nd highest salary give n=1
for 3rd n=2 like that.)

To find nth highest salary

SELECT * FROM Employee E1 WHERE n-1 =
(SELECT COUNT(DISTINCT Salary) FROM Employee E2 WHERE E1.Salary < E2.Salary)

To find 2nd highest salary

SELECT * FROM Employee E1 WHERE 1 =
(SELECT COUNT(DISTINCT Salary) FROM Employee E2 WHERE E1.Salary < E2.Salary)

select top 2 * from Trainee where Salary in(select top 1 Salary from Depart)order by Salary DESC

To find 2nd lowest salary

SELECT * FROM Employee E1 WHERE 1 =
(SELECT COUNT(DISTINCT Salary) FROM Employee E2 WHERE E1.Salary > E2.Salary)

To find nth lowest salary

SELECT * FROM Employee E1 WHERE n-1 =
(SELECT COUNT(DISTINCT Salary) FROM Employee E2 WHERE E1.Salary > E2.Salary)