> For the complete documentation index, see [llms.txt](https://mariadb.com/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mariadb.com/docs/server/reference/sql-statements/data-manipulation/selecting-data/set-operations/precedence-control-in-table-operations.md).

# Precedence Control in Table Operations

You can control the ordering of execution on table operations using parentheses.

## Syntax

```bnf
(  expression )
[ORDER BY [column[, column...]]]
[LIMIT {[offset,] row_count | row_count OFFSET offset}]
```

## Description

Using parentheses in SQL allows to control the order of execution for [SELECT](/docs/server/reference/sql-statements/data-manipulation/selecting-data/select.md) statements and [Table Value Constructor](/docs/server/reference/sql-structure/sql-language-structure/table-value-constructors.md), including [UNION](/docs/server/reference/sql-statements/data-manipulation/selecting-data/set-operations/union.md), [EXCEPT](/docs/server/reference/sql-statements/data-manipulation/selecting-data/set-operations/except.md), and [INTERSECT](/docs/server/reference/sql-statements/data-manipulation/selecting-data/set-operations/intersect.md) operations. MariaDB executes the parenthetical expression before the rest of the statement. You can then use [ORDER BY](/docs/server/reference/sql-statements/data-manipulation/selecting-data/order-by.md) and [LIMIT](/docs/server/reference/sql-statements/data-manipulation/selecting-data/limit.md) clauses the further organize the result set.

{% hint style="info" %}
The Optimizer may rearrange the exact order in which MariaDB executes different parts of the statement. When it calculates the result set, however, it returns values as though the parenthetical expression were executed first.
{% endhint %}

## Example

```sql
CREATE TABLE test.t1 (num INT);

INSERT INTO test.t1 VALUES (1),(2),(3);

(SELECT * FROM test.t1 
 UNION 
 VALUES (10)) 
INTERSECT 
VALUES (1),(3),(10),(11);
+------+
| num  |
+------+
|    1 |
|    3 |
|   10 |
+------+

((SELECT * FROM test.t1 
  UNION 
  VALUES (10)) 
 INTERSECT 
 VALUES (1),(3),(10),(11)) 
ORDER BY 1 DESC;
+------+
| num  |
+------+
|   10 |
|    3 |
|    1 |
+------+
```

<sub>*This page is licensed: CC BY-SA / Gnu FDL*</sub>

{% @marketo/form formId="4316" %}


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