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42 lines
940 B
Markdown
42 lines
940 B
Markdown
# Between Symmetric
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PostgreSQL's `between` construct allows you to make a comparison _between_
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two values (numbers, timestamps, etc.).
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```sql
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> select * from generate_series(1,10) as numbers(a) where numbers.a between 3 and 6;
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a
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---
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3
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4
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5
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6
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```
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If you supply an empty range by using the larger of the two values first, an
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empty set will result.
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```sql
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> select * from generate_series(1,10) as numbers(a) where numbers.a between 6 and 3;
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a
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---
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```
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Tacking `symmetric` onto the `between` construct is one way to avoid this
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issue.
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```sql
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> select * from generate_series(1,10) as numbers(a) where numbers.a between symmetric 6 and 3;
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a
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---
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3
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4
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5
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6
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```
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> BETWEEN SYMMETRIC is the same as BETWEEN except there is no requirement
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> that the argument to the left of AND be less than or equal to the argument
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> on the right. If it is not, those two arguments are automatically swapped,
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> so that a nonempty range is always implied.
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