SUBSTRING function in Amazon QLDB - Amazon Quantum Ledger Database (Amazon QLDB)
SyntaxArgumentsReturn typeExamplesRelated functions

SUBSTRING function in Amazon QLDB

Important

End of support notice: Existing customers will be able to use Amazon QLDB until end of support on 07/31/2025. For more details, see Migrate an Amazon QLDB Ledger to Amazon Aurora PostgreSQL.

In Amazon QLDB, use the SUBSTRING function to return a substring from a given string. The substring starts from the specified start index and ends at the last character of the string, or at the specified length.

Syntax

SUBSTRING ( string, start-index [, length ] )

Arguments

string

The field name or expression of data type string from which to extract a substring.

start-index

The start position within the string from which to begin the extraction. This number can be negative.

The first character of string has an index of 1.

length

(Optional) The number of characters (code points) to extract from the string, starting at start-index and ending at (start-index + length) - 1. In other words, the length of the substring. This number can't be negative.

If this parameter is not provided, the function proceeds until the end of the string.

Return type

string

Examples

SUBSTRING('123456789', 0)      -- '123456789'
SUBSTRING('123456789', 1)      -- '123456789'
SUBSTRING('123456789', 2)      -- '23456789'
SUBSTRING('123456789', -4)     -- '123456789'
SUBSTRING('123456789', 0, 999) -- '123456789'
SUBSTRING('123456789', 0, 2)   -- '1'
SUBSTRING('123456789', 1, 999) -- '123456789'
SUBSTRING('123456789', 1, 2)   -- '12'
SUBSTRING('1', 1, 0)           -- ''
SUBSTRING('1', 1, 0)           -- ''
SUBSTRING('1', -4, 0)          -- ''
SUBSTRING('1234', 10, 10)      -- ''

-- Runnable statements
SELECT SUBSTRING('123456789', 1) FROM << 0 >>    -- "123456789"
SELECT SUBSTRING('123456789', 1, 2) FROM << 0 >> -- "12"

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