#使用Oracle数据库

CREATE PROCEDURE RemoveNotNullConstraintsExceptPrimaryKey()
BEGIN
    DECLARE done INT DEFAULT FALSE;
    DECLARE tbl_name VARCHAR(255);
    DECLARE cur CURSOR FOR SELECT TABLE_NAME FROM information_schema.TABLES WHERE TABLE_SCHEMA = DATABASE();
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;

    OPEN cur;

    read_loop: LOOP
        FETCH cur INTO tbl_name;
        IF done THEN
            LEAVE read_loop;
        END IF;

        -- 构建 ALTER 语句，排除主键列
        SET @alter_sql = (
            SELECT GROUP_CONCAT(CONCAT('MODIFY ', COLUMN_NAME, ' ', COLUMN_TYPE, ' NULL'))
            FROM information_schema.COLUMNS
            WHERE TABLE_SCHEMA = DATABASE()
            AND TABLE_NAME = tbl_name
            AND IS_NULLABLE = 'NO'
            AND COLUMN_KEY != 'PRI'
        );

        -- 执行修改表结构的 SQL
        IF @alter_sql IS NOT NULL THEN
            SET @full_alter_sql = CONCAT('ALTER TABLE ', tbl_name, ' ', @alter_sql);
            PREPARE stmt FROM @full_alter_sql;
            EXECUTE stmt;
            DEALLOCATE PREPARE stmt;
        END IF;

    END LOOP;

    CLOSE cur;
END //

DELIMITER ;

-- 调用存储过程
SET FOREIGN_KEY_CHECKS = 0;
CALL RemoveNotNullConstraintsExceptPrimaryKey();