OVERLAY

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Syntax

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Scalar

overlay(value PLACING replacement FROM start [FOR count])

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Arguments

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Returns

• Type: STRING
• Possible values: The unchanged prefix, replacement, and remaining suffix.
• NULL behavior: Returns NULL when any supplied operand is NULL.

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Properties

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Usage notes

• Positions and replacement counts use Unicode characters rather than UTF-8 bytes. Start beyond the input appends the replacement. Count zero inserts without removing characters.

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Examples

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Example values

SELECT overlay('Txxxxas' PLACING 'hom' FROM 2 FOR 4) AS "value";

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Insert without replacing characters

SELECT overlay('abcd' PLACING '-' FROM 3 FOR 0) AS inserted;

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Limitations

• Start must be at least 1; smaller values raise an error. Use a nonnegative count. A negative count can duplicate parts of the input. These forms cover STRING inputs only.