Why is character "A" used in select instead of "*"?-CodePudding

In a groovy application the query contains just a letter in the select.

Example: SELECT a FROM Employee a WHERE a.emplID =123456

My question is that the same as: SELECT * FROM Employee WHERE emplId=123456

If not what is the above query doing?

CodePudding user response：

a in this case is an alias to the Employee table.

An alias is declared in the FROM statement, then referenced in the SELECT statement.

SELECT a
FROM Employee a

This is basically the same as:

SELECT *
FROM Employee

If you want to reference specific columns when using an alias, it would be done like this:

SELECT a.ID, a.Name, a.Salary
FROM Employee a

Hope this helps

CodePudding user response：

In your example a represents the Employee data, and is the same as saying Employee.*. So, yes it's the same as selecting all the data being returned by that query.