# Subqueries With EXISTS

## Syntax

```sql
SELECT ... WHERE EXISTS <Table subquery>
```

## Description

[Subqueries](https://mariadb.com/docs/server/reference/sql-statements/data-manipulation/selecting-data/subqueries) using the `EXISTS` keyword will return `true` if the subquery returns any rows. Conversely, subqueries using `NOT EXISTS` will return `true` only if the subquery returns no rows from the table.

EXISTS subqueries ignore the columns specified by the [SELECT](https://mariadb.com/docs/server/reference/sql-statements/data-manipulation/selecting-data/select) of the subquery, since they're not relevant. For example,

```sql
SELECT col1 FROM t1 WHERE EXISTS (SELECT * FROM t2);
```

and

```sql
SELECT col1 FROM t1 WHERE EXISTS (SELECT col2 FROM t2);
```

produce identical results.

## Examples

```sql
CREATE TABLE sq1 (num TINYINT);

CREATE TABLE sq2 (num2 TINYINT);

INSERT INTO sq1 VALUES(100);

INSERT INTO sq2 VALUES(40),(50),(60);

SELECT * FROM sq1 WHERE EXISTS (SELECT * FROM sq2 WHERE num2>50);
+------+
| num  |
+------+
|  100 |
+------+

SELECT * FROM sq1 WHERE NOT EXISTS (SELECT * FROM sq2 GROUP BY num2 HAVING MIN(num2)=40);
Empty set (0.00 sec)
```

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