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30 lines
730 B
Markdown
30 lines
730 B
Markdown
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# EXISTS {#exists-operator}
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The `EXISTS` operator tests 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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!!! 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:
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``` sql
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SELECT 'Exists' WHERE EXISTS (SELECT * FROM numbers(10) WHERE number < 2);
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SELECT 'Empty subquery' WHERE EXISTS (SELECT * FROM numbers(10) WHERE number > 12);
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```
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The first query returns one row. The second query does not return rows because the result of the subquery is empty.
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``` text
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┌─'Exists'─┐
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│ Exists │
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└──────────┘
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```
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