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The existing documentation for EXISTS makes it look like it only works as part of a WHERE clause, when in fact, it can be used in many places. Changing the docs to note that a bit differently with another example should provide more clarity on the use of this term.
63 lines
1.4 KiB
Markdown
63 lines
1.4 KiB
Markdown
---
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slug: /en/sql-reference/operators/exists
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---
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# EXISTS
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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 also be used in a [WHERE](../../sql-reference/statements/select/where.md) clause.
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:::tip
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References to main query tables and columns are not supported in a subquery.
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:::
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**Syntax**
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``` sql
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EXISTS(subquery)
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```
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**Example**
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Query checking existence of values in a subquery:
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``` sql
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SELECT EXISTS(SELECT * FROM numbers(10) WHERE number > 8), EXISTS(SELECT * FROM numbers(10) WHERE number > 11)
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```
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Result:
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``` text
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┌─in(1, _subquery1)─┬─in(1, _subquery2)─┐
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│ 1 │ 0 │
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└───────────────────┴───────────────────┘
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```
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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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