Sub query can be used to a get data from another database table along with current database table used in the main query.
SELECT FullName = (SELECT FirstName + ' ' + LastName FROM PersonalDetails WHERE PersonalDetailsId =
ac.PersonalDetailsId), Salary, PPFDeduction, NetSalary FROM Accounts ac
Above query returns
PersonalDetails table (combination of FirstName and LastName) and Salary, PPFDeduction and NetSalary from
Accounts table. Notice the alias “ac” used for Accounts table.
In case, no records found in PersonalDetails table, null value would be returned for FullName column.Views: 6697 | Post Order: 48