如何在mysql中选择可选列？

Question

I want to run a query on my MYSQL database. Depending on what the values are, I want to select different fields.

For example, if field 'e' is null, then I want to SELECT fields a,b,c,d. If field 'e' is not null, then I want so SELECT fields a,b,c,d,e.

Something along the lines of

response = SELECT a,b,c,d (AND e IF e IS NOT NULL) FROM table1 WHERE id = 1;

Answer 1

The number of columns in a query result set cannot change. You can't return four columns on some rows and five columns on other rows from a given query.

You'll just have to write your application code with a condition to ignore the fifth column if it's null.