可以使用子查询在 MySql 查询中分配 LIMIT 值吗？

Question

I need extract de last rows of a table without no order. I Try this but don't function:

SELECT * 
FROM contabilidad.emp001_series
LIMIT (SELECT COUNT(*)-10 AS TOTAL FROM contabilidad.emp001_series)

I need the result in natural order and can't use ORDER BY

Answer 1

No. Subqueries are not allowed.

Further, there is no such thing as "natural" order in a SQL table. SQL tables represent unordered sets.

Your best bet is to do a reverse sort and start at the 11th row:

select s.*
from contabilidad.emp001_series s
order by id desc
limit 999999999 offset 10;

If you want an arbitrary set of ids, you could also use:

select s.*
from contabilidad.emp001_series s
where id < (select s2.id
            from contabilidad.emp001_series s2
            order by s2.id desc
            limit 1 offset 10
           );

Both of these assume you have a column of some sort that specifies the ordering.

Answer 2

https://dev.mysql.com/doc/refman/8.0/en/select.html has detailed documentation about MySQL's SELECT statement including all its clauses.

It says:

The LIMIT clause can be used to constrain the number of rows returned by the SELECT statement. LIMIT takes one or two numeric arguments, which must both be nonnegative integer constants, with these exceptions:

• Within prepared statements, LIMIT parameters can be specified using? placeholder markers.

• Within stored programs, LIMIT parameters can be specified using integer-valued routine parameters or local variables.

Expressions, including subqueries, are not mentioned as legal argument in the LIMIT clause.

A simple solution would be to do your task in two queries: the first to get the COUNT() and then use that value as a constant value in the second query that includes the LIMIT.

Not every task needs to be done in a single SQL statement.