Zipping Arrays in PostgreSQL
In PostgreSQL, combining two arrays of equal length into pairs can be achieved using various methods.
Versions 9.5 and Later:
Postgres version 9.5 introduced the array_agg function with the ROWS FROM construct, which allows for direct concatenation of arrays:
SELECT ARRAY[a,b] AS ab FROM unnest('{a,b,c}'::text[], '{d,e,f}'::text[]) x(a,b);
Versions 9.4 and Older:
Prior to 9.5, there are two approaches:
Simple Zipping:
For arrays with the same number of elements, use the following query:
SELECT ARRAY[a,b] AS ab FROM ( SELECT unnest('{a,b,c}'::text[]) AS a , unnest('{d,e,f}'::text[]) AS b ) x;
Zipping for Multi-Dimensional Arrays:
To convert the zipped arrays into a multi-dimensional array, consider the following custom aggregate function:
CREATE AGGREGATE array_agg_mult (anyarray) ( SFUNC = array_cat , STYPE = anyarray , INITCOND = '{}' );
Use this aggregate function with the unnest operation:
SELECT array_agg_mult(ARRAY[ARRAY[a,b]]) AS ab FROM ( SELECT unnest('{a,b,c}'::text[]) AS a , unnest('{d,e,f}'::text[]) AS b ) x;
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