SQL-Important Sql table Queries

1.how to check sql server version
Ans-select @@version

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2.how to check how many tables
Ans-select * from sys.tables

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3.how to show complete structure of table
Ans-EXEC sp_help TableName;

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4.How to show all temp tables in sql server
Ans-select * from tempdb.sys.objects

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5.How to list all indexes
SELECT T.Name, I.name FROM sys.indexes I INNER JOIN Sys.tables t ON t.object_id = I.Object_ID WHERE index_id >= 1 -- skip heep

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6.How to list all indexes with all details
select * from sys.indexes

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7.How to get first and last date of month
DECLARE @Month int
DECLARE @Year int

set @Month = 2
set @Year = 2005

select DATEADD(month,@Month-1,DATEADD(year,@Year-1900,0)) /*First*/

select DATEADD(day,-1,DATEADD(month,@Month,DATEADD(year,@Year-1900,0))) /*Last*/


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8.Display every Nth row

Query:
SELECT id
FROM employees
GROUP BY id
HAVING MOD(id, N) = 0;

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9.Age in years

DECLARE @dob  datetime
SET @dob='1992-01-09 00:00:00'

SELECT DATEDIFF(hour,@dob,GETDATE())/8766.0 AS AgeYearsDecimal
    ,CONVERT(int,ROUND(DATEDIFF(hour,@dob,GETDATE())/8766.0,0)) AS AgeYearsIntRound
    ,DATEDIFF(hour,@dob,GETDATE())/8766 AS AgeYearsIntTrunc

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10.Date diffrence

DATEDIFF(datepart,startdate,enddate)

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11.Update Table using Join

UPDATE employee e LEFT JOIN employee_salary s ON e.id=s.employee_id
SET s.salary='50000'
where e.first_name='Admin'