@(一只心中无码的程序员)专栏
叨叨两句
- ~
SQL习题041
将所有to_date为9999-01-01的全部更新为NULL,且 from_date更新为2001-01-01。
CREATE TABLE IF NOT EXISTS titles_test (id int(11) not null primary key,emp_no int(11) NOT NULL,title varchar(50) NOT NULL,from_date date NOT NULL,to_date date DEFAULT NULL);insert into titles_test values ('1', '10001', 'Senior Engineer', '1986-06-26', '9999-01-01'),
('2', '10002', 'Staff', '1996-08-03', '9999-01-01'),('3', '10003', 'Senior Engineer', '1995-12-03', '9999-01-01'),('4', '10004', 'Senior Engineer', '1995-12-03', '9999-01-01'),('5', '10001', 'Senior Engineer', '1986-06-26', '9999-01-01'),('6', '10002', 'Staff', '1996-08-03', '9999-01-01'),('7', '10003', 'Senior Engineer', '1995-12-03', '9999-01-01');用 UPDATE 语句更新若干列的最基本用法，详细可参考：http://www.w3school.com.cn/sql/sql_update.asphttps://www.w3schools.com/sql/sql_update.asp另外要注意若干列 to_date = NULL 和 from_date = '2001-01-01' 之间只能用逗号连接，切勿用 AND 连接。UPDATE titles_test SET to_date = NULL, from_date = '2001-01-01'WHERE to_date = '9999-01-01';