REPEAT

Return the input string repeated n times.

Category: stringReturns: VARCHARDialect: Standard

Syntax

REPEAT(str, n)

Description

## Overview Returns the result of concatenating the input string with itself `n` times. REPEAT is useful for generating separator lines, producing test fixtures of a known length, and building indented text output for reports. For large repetition counts or for constructing huge strings, consider whether a single CONCAT or an aggregate is more appropriate. The result length grows linearly with `n` and the cost is proportional to the output size. ## Behavior - Returns NULL when any argument is NULL. - If `n` is 0 or negative, returns an empty string. - If the input string is empty, returns an empty string regardless of `n`. - Operates on Unicode code points; multi-byte characters are preserved intact. - No upper bound is enforced on the result size, but very large repetitions consume memory proportional to the output. - Equivalent to SPACE(n) when the input is a single space character. ## Compatibility - Widely supported across SQL dialects with matching semantics.

Parameters

Name	Type	Description
`str`		Specifies the string to repeat.
`n`		Specifies the number of times to concatenate the string. Zero or negative values yield an empty string.

Examples

-- Repeat three times
SELECT REPEAT('ab', 3);  -- 'ababab'

-- Zero repetitions returns empty
SELECT REPEAT('hello', 0);  -- ''

-- Negative count returns empty
SELECT REPEAT('x', -2);  -- ''

-- NULL propagates
SELECT REPEAT(CAST(NULL AS VARCHAR), 3);  -- NULL

-- Build a separator row for a text report
SELECT REPEAT('-', 40) AS divider;

-- Generate test strings of a target length
SELECT REPEAT('x', 256) AS long_test_string;

Pitfalls

REPEAT can produce very large strings quickly. REPEAT(' ', 1e9) allocates a gigabyte. Validate the count argument when it is driven by user input.
REPEAT of an empty string always returns an empty string, regardless of n. This is not an error, but it can mask bugs where the input was accidentally trimmed.
REPEAT counts by code points. A multi-byte character repeated N times produces output whose byte length is N times the code point's UTF-8 width.
REPEAT is not the same as LPAD/RPAD. REPEAT cannot fill to an exact target length unless you chain it with SUBSTRING.