What’s wrong with this query?

Tags

query, sub-query, table alias

Recently there was a question on one of the MS SQL forum, the query which user had posted was pretty simple but was behaving strangely.
Here I’m demonstrating you all the scenario which user had posted.

Create two tables and inserted few records in both the tables.

DECLARE @Header Table (EmpId Int , FirstName Varchar(50) , LastName Varchar(50))
DECLARE @Detail Table (id Int , Department Varchar(50))

INSERT INTO @Header Values(1 , 'ABC' , 'CBA'), (2 , 'BCD' , 'DCB'),(3 , 'CDE' , 'EDC')
INSERT INTO @Detail Values(7 , 'IT'), (8 , 'HR'),(9 , 'Admin')

Now execute below query, which pulls records from Header table for matching EmpId exists in Detail table.

SELECT * FROM @Header WHERE EmpId IN (SELECT EMPID From @Detail)

Following is the result set generated by above query.

Is this query pulling out right data?

Apparently, yes it does, but wait a minute and carefully observe the sub-query.

SELECT EMPID From @Detail

If you carefully check the Detail table definition it doesn’t have any EMPID column defined, infact it has column name ID, but still entire query runs successfully and produces the result.

The EMPID in the sub-query does refer to the outer-query (Header) EMPID column and we are getting the result set.

Alter the above query introduce table alias and run it again.

SELECT * FROM @Header H WHERE H.EmpId IN (SELECT D.EMPID From @Detail D)

Now, the query fails with the error message.

Msg 207, Level 16, State 1, Line 7
Invalid column name ‘EMPID’.

Many a times we do commit this kind of coding errors in our queries without realising it, so it’s always recommended to use table alias’s in your queries to overcome this.

Hope this helps.!!!

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List permissions on any object – SQL Server

Tags

object permission, permission, sp_helprotect

Sometimes we need to quickly check the permissions on any database object, below script will help you to extract this information.

Method 1.

USE <DB_Name , Sysname , Database Name>
Go
sp_helprotect '<object name , sysname , object name>'

Note: use Ctrl-Shift-M to replace template parameters.

Though the above method displays the desired result we can not filter the result, to filter the result based on different parameters there is an alternative method as shown below.

Method 2.

USE <DB_Name , Sysname , Database Name>
Go
SELECT
    dp.NAME AS principal_name
    ,dp.type_desc AS principal_type_desc
    ,o.NAME AS object_name
    ,o.type_desc
    ,p.permission_name
    ,p.state_desc AS permission_state_desc
    FROM sys.all_objects o
    INNER JOIN sys.database_permissions p ON o.OBJECT_ID=p.major_id
    LEFT OUTER JOIN sys.database_principals dp ON p.grantee_principal_id = dp.principal_id
    WHERE o.NAME = '<object name , sysname ,object name>' 
    --AND dp.name = '<principal name , sysname ,login name>'    

Note: use Ctrl-Shift-M to replace template parameters.

Hope this helps…!