运行保存在字段中的SQL查询

Question

I have a follow up question on the link below. Apparently I have to create a new question (Sorry if I should not, I am new to stackoverflow)

One of the responses to the issue was this:

SELECT sql_text INTO @sql FROM sql_queries WHERE id = 1;
PREPARE sql_query FROM @sql;
EXECUTE sql_query;

It helped if I run the above line by line, but I want to run this as a whole and use the result in another query. So my issue is the following:

1 - It doesn't work if I remove the semicolons and try to run the three lines at the same time.

2 - How can I read the results of this run into a query. I was thinking of putting all three lines in a subquery, but that didn't work.

I appreciate if you have any comment on those. Thanks!

OriginalQuestion

Answer 1

I do not think you can "embed" an execute (nor it's results) in another query, which is what it sounds like what your goal is. Instead you might want to consider building your final query with the @sql query as a subquery like:

SET @finalSQL = CONCAT("SELECT stuff FROM sometables JOIN (", @sql, ") AS subQ ON blah");
PREPARE sql_query FROM @sql;
EXECUTE sql_query;

Of course, you need to make a lot of assumptions about the @sql query you've been provided; at minimum you must assume: it will be valid for the join conditions (or however the subquery is used) and that it is not terminated with a semi-colon. The latter can be easily checked and remedied, the former could require a significant amount of parsing and analysis.