SQL Server是否可以使用PHP从UNION查询返回不同的别名列名？

Question

I have several SELECT queries in a UNION statement (or UNION ALL ). As it is a UNION it is going to return the single dataset with one column (I only have one value return in this case), typically the column name from the first query.

I aliased the columns in each query, so I can use the data by name instead of index in my PHP script.

Is it possible to get the individual column names aliased from each individual SELECT ?

Consider,

SELECT name as manager FROM employees WHERE type = 1
UNION
SELECT name as mid_level_manager FROM employees WHERE type = 2
UNION
SELECT name as regular_employee FROM employees WHERE type = 3

I am using PDO with Prepared Statements, like this,

$results = $prepared_statement->fetchAll(PDO::FETCH_ASSOC);

Maybe not the best example, but how could I get those aliased column names? Query works fine in and of itself. I am using SQL Server 2012.

Answer 1

You can't. A UNION is going to use the aliased column name from the first query (I think, it might be the last). That's the point of a UNION.

You can select multiple columns and alias each one, but you can't have a different column alias for different rows , that does not make sense.

Answer 2

There's only a single name for a single column, but you might add the type column indicating which select returned that row:

SELECT type, name as manager FROM employees WHERE type = 1
UNION
SELECT type, name as mid_level_manager FROM employees WHERE type = 2
UNION
SELECT type, name as regular_employee FROM employees WHERE type = 3