sql přidat vypočítaný sloupec
-- MySQL / Oracle:
ALTER TABLE table_name ADD double_count NUMBER(10, 2)
GENERATED ALWAYS AS (account * 2) VIRTUAL;
-- SQL Server
ALTER TABLE table_name ADD [double_count] AS (account * 2);
sql alter tabulka add sloupec, pokud existuje
IF NOT EXISTS (
SELECT
*
FROM
INFORMATION_SCHEMA.COLUMNS
WHERE
TABLE_NAME = 'table_name' AND COLUMN_NAME = 'col_name')
BEGIN
ALTER TABLE table_name
ADD col_name data_type NULL
END;