In a join, how to prefix all column names with the table it came from

Question

I\'m analysing a rather horrible legacy database/codebase, trying to reduce server load by combining queries into joins (including an email alert cron job that typically inv

Answer 1

I ended up just building the field set for the query, as as of 2020 this still isn't supported.

But, being a lazy programmer, I obviously didn't want to manually type this all out for all of the tables in my query. So I wrote a query to build the select statement:

SELECT
    CONCAT(table_name, ".", column_name, " AS ", CHAR(34), table_name, ".", column_name, CHAR(34)) field_names
FROM
    information_schema.columns
WHERE
    table_schema = "my_database"
    AND table_name IN(
        "table_1",
        "table_2"
    );

which will output something like:

| field_names                        |
|------------------------------------|
| table_1.id AS "table_1.id"         |
| table_1.name AS "table_1.name"     |
| table_2.id AS "table_2.id"         |
| table_2.number AS "table_2.number" |

That can then easily be copied into your SELECT statement.