# Subqueries

{% columns %}
{% column %}
{% content-ref url="subqueries/subqueries-and-all" %}
[subqueries-and-all](https://mariadb.com/docs/server/reference/sql-statements/data-manipulation/selecting-data/subqueries/subqueries-and-all)
{% endcontent-ref %}
{% endcolumn %}

{% column %}
Compare a value against all results from a subquery. The `ALL` operator returns `TRUE` if the comparison holds for every row returned by the subquery.
{% endcolumn %}
{% endcolumns %}

{% columns %}
{% column %}
{% content-ref url="subqueries/subqueries-and-any" %}
[subqueries-and-any](https://mariadb.com/docs/server/reference/sql-statements/data-manipulation/selecting-data/subqueries/subqueries-and-any)
{% endcontent-ref %}
{% endcolumn %}

{% column %}
Compare a value against any result from a subquery. The `ANY` (or `SOME`) operator returns `TRUE` if the comparison holds for at least one row. `IN` can be used for `=ANY`.
{% endcolumn %}
{% endcolumns %}

{% columns %}
{% column %}
{% content-ref url="subqueries/subqueries-and-exists" %}
[subqueries-and-exists](https://mariadb.com/docs/server/reference/sql-statements/data-manipulation/selecting-data/subqueries/subqueries-and-exists)
{% endcontent-ref %}

{% endcolumn %}

{% column %}
Test for the existence of rows. The `EXISTS` operator returns `TRUE` if the subquery returns at least one row, often used for correlated subqueries.
{% endcolumn %}
{% endcolumns %}

{% columns %}
{% column %}
{% content-ref url="subqueries/subqueries-and-joins" %}
[subqueries-and-joins](https://mariadb.com/docs/server/reference/sql-statements/data-manipulation/selecting-data/subqueries/subqueries-and-joins)
{% endcontent-ref %}
{% endcolumn %}

{% column %}
Understand when to use subqueries versus joins. This guide explains performance implications and how to rewrite subqueries as joins for efficiency.
{% endcolumn %}
{% endcolumns %}

{% columns %}
{% column %}
{% content-ref url="subqueries/subqueries-in-a-from-clause-derived-tables" %}
[subqueries-in-a-from-clause-derived-tables](https://mariadb.com/docs/server/reference/sql-statements/data-manipulation/selecting-data/subqueries/subqueries-in-a-from-clause-derived-tables)
{% endcontent-ref %}
{% endcolumn %}

{% column %}
Use a subquery as a temporary table. Derived tables allow you to select from the result set of another query within the `FROM` clause.
{% endcolumn %}
{% endcolumns %}

{% columns %}
{% column %}
{% content-ref url="subqueries/subqueries-row-subqueries" %}
[subqueries-row-subqueries](https://mariadb.com/docs/server/reference/sql-statements/data-manipulation/selecting-data/subqueries/subqueries-row-subqueries)
{% endcontent-ref %}
{% endcolumn %}

{% column %}
Retrieve a single row of multiple values. A row subquery returns a tuple that can be compared against a row constructor in the outer query.
{% endcolumn %}
{% endcolumns %}

{% columns %}
{% column %}
{% content-ref url="subqueries/subqueries-scalar-subqueries" %}
[subqueries-scalar-subqueries](https://mariadb.com/docs/server/reference/sql-statements/data-manipulation/selecting-data/subqueries/subqueries-scalar-subqueries)
{% endcontent-ref %}
{% endcolumn %}

{% column %}
Return a single value. A scalar subquery produces a one-row, one-column result that can be used anywhere a constant or expression is valid.
{% endcolumn %}
{% endcolumns %}

{% columns %}
{% column %}
{% content-ref url="subqueries/subquery-limitations" %}
[subquery-limitations](https://mariadb.com/docs/server/reference/sql-statements/data-manipulation/selecting-data/subqueries/subquery-limitations)
{% endcontent-ref %}
{% endcolumn %}

{% column %}
Review restrictions on subquery usage. This page details unsupported operations, such as modifying a table while selecting from it in a subquery.
{% endcolumn %}
{% endcolumns %}