postgresql语法使用

--数组：
SELECT (ARRAY['{101, 111, 121}', '{201, 211, 221}'])[1]::text[];
SELECT (ARRAY['{101, 111, 121}', '{201, 211, 221}'])::text[];

SELECT (ARRAY['{101, 111, 121}', '{201, 211, 221}'])[1]::text[];
SELECT (ARRAY['{101, 111, 121}'::int[], '{201, 211, 221}'])::int[];
SELECT (ARRAY['{101, 111, 121}'::int[], '{201, 211, 221}'])[1][1];
SELECT (ARRAY['{{101, 111, 121},{201, 211, 221}}'])[1];
SELECT (ARRAY['{{101, 111, 121},{201, 211, 221}}'])[1]::int[];