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45 lines
940 B
Markdown
45 lines
940 B
Markdown
# EXISTS {#exists-operator}
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The `EXISTS` operator checks how many records are in the result of a subquery. If it is empty, then the operator returns `0`. Otherwise, it returns `1`.
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`EXISTS` can be used in a [WHERE](../../sql-reference/statements/select/where.md) clause.
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!!! warning "Warning"
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References to main query tables and columns are not supported in a subquery.
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**Syntax**
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```sql
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WHERE EXISTS(subquery)
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```
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**Example**
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Query with a subquery returning several rows:
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``` sql
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SELECT count() FROM numbers(10) WHERE EXISTS(SELECT number FROM numbers(10) WHERE number > 8);
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```
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Result:
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``` text
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┌─count()─┐
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│ 10 │
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└─────────┘
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```
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Query with a subquery that returns an empty result:
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``` sql
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SELECT count() FROM numbers(10) WHERE EXISTS(SELECT number FROM numbers(10) WHERE number > 11);
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```
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Result:
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``` text
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┌─count()─┐
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│ 0 │
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└─────────┘
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```
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