MySQL 8.0 Reference Manual Including MySQL NDB Cluster 8.0
In general, you cannot modify a table and select from the same table in a subquery. For example, this limitation applies to statements of the following forms:
DELETE FROM t WHERE ... (SELECT ... FROM t ...);
UPDATE t ... WHERE col = (SELECT ... FROM t ...);
{INSERT|REPLACE} INTO t (SELECT ... FROM t ...);
Exception: The preceding prohibition does not apply if for the modified table you are using a derived table and that derived table is materialized rather than merged into the outer query. (See Section 10.2.2.4, “Optimizing Derived Tables, View References, and Common Table Expressions with Merging or Materialization”.) Example:
UPDATE t ... WHERE col = (SELECT * FROM (SELECT ... FROM t...) AS dt ...);
Here the result from the derived table is materialized as a
temporary table, so the relevant rows in
t have already been selected by the time
the update to t takes place.
In general, you may be able to influence the optimizer to
materialize a derived table by adding a
NO_MERGE optimizer hint.
See Section 10.9.3, “Optimizer Hints”.
Row comparison operations are only partially supported:
For expr [NOT] IN
subqueryexpr can be an
n-tuple (specified using row
constructor syntax) and the subquery can return rows of
n-tuples. The permitted
syntax is therefore more specifically expressed as
row_constructor
[NOT] IN
table_subquery
For expr
op {ALL|ANY|SOME}
subqueryexpr must be a scalar value
and the subquery must be a column subquery; it cannot
return multiple-column rows.
In other words, for a subquery that returns rows of
n-tuples, this is supported:
(expr_1, ...,expr_n) [NOT] INtable_subquery
But this is not supported:
(expr_1, ...,expr_n)op{ALL|ANY|SOME}subquery
The reason for supporting row comparisons for
IN but not for the others is that
IN is implemented by rewriting it as a
sequence of =
comparisons and AND operations.
This approach cannot be used for ALL,
ANY, or SOME.
Prior to MySQL 8.0.14, subqueries in the
FROM clause cannot be correlated
subqueries. They are materialized in whole (evaluated to
produce a result set) during query execution, so they cannot
be evaluated per row of the outer query. The optimizer
delays materialization until the result is needed, which may
permit materialization to be avoided. See
Section 10.2.2.4, “Optimizing Derived Tables, View References, and Common Table Expressions
with Merging or Materialization”.
MySQL does not support LIMIT in
subqueries for certain subquery operators:
mysql>SELECT * FROM t1WHERE s1 IN (SELECT s2 FROM t2 ORDER BY s1 LIMIT 1);ERROR 1235 (42000): This version of MySQL doesn't yet support 'LIMIT & IN/ALL/ANY/SOME subquery'
MySQL permits a subquery to refer to a stored function that
has data-modifying side effects such as inserting rows into
a table. For example, if f() inserts
rows, the following query can modify data:
SELECT ... WHERE x IN (SELECT f() ...);
This behavior is an extension to the SQL standard. In MySQL,
it can produce nondeterministic results because
f() might be executed a different number
of times for different executions of a given query depending
on how the optimizer chooses to handle it.
For statement-based or mixed-format replication, one implication of this indeterminism is that such a query can produce different results on the source and its replicas.