目录
1、构造一个触发器audit_log,在向employees_test表中插入一条数据的时候,触发插入相关的数据到audit中。
2、删除emp_no重复的记录,只保留最小的id对应的记录。
3、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。
4、将id=5以及emp_no=10001的行数据替换成id=5以及emp_no=10005,其他数据保持不变,使用replace实现。
5、将titles_test表名修改为titles_2017。
总结
1、构造一个触发器audit_log,在向employees_test表中插入一条数据的时候,触发插入相关的数据到audit中。
CREATE TABLE employees_test(
ID INT PRIMARY KEY NOT NULL,
NAME TEXT NOT NULL,
AGE INT NOT NULL,
ADDRESS CHAR(50),
SALARY REAL
);
CREATE TABLE audit(
EMP_no INT NOT NULL,
NAME TEXT NOT NULL
);
答案:
create trigger audit_log
after insert on employees_test
begin
insert into audit values(new.id,new.name);
end;
2、删除emp_no重复的记录,只保留最小的id对应的记录。
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');
答案:
delete from titles_test
where id not in (
select min(id) from titles_test
group by emp_no
);
3、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');
答案:
update titles_test
set to_date=NULL, from_date='2001-01-01'
where to_date='9999-01-01'
4、将id=5以及emp_no=10001的行数据替换成id=5以及emp_no=10005,其他数据保持不变,使用replace实现。
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');
答案:
update titles_test
set emp_no=10005
where id=5
and emp_no=10001;
5、将titles_test表名修改为titles_2017。
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');
答案:
alter table titles_test
rename to titles_2017;
总结
(1)触发器
基本语法如下:在这里,event_name 可以是在所提到的表 table_name 上的 INSERT、DELETE 和 UPDATE 数据库操作。可以在表名后选择指定 FOR EACH ROW。CREATE TRIGGER trigger_name [BEFORE|AFTER] event_name ON table_name BEGIN -- 触发器逻辑.... END;
CREATE TRIGGER trigger_name [BEFORE|AFTER] UPDATE OF column_name ON table_name BEGIN -- 触发器逻辑.... END;
(2)SQLite Delete 语句
基本语法如下:DELETE FROM table_name WHERE [condition];
(3)SQLite Update 语句
基本语法如下:UPDATE table_name SET column1 = value1, column2 = value2...., columnN = valueN WHERE [condition];
(4)SQLite Alter 命令
对已有表进行更名:在已有表增加新的列:ALTER TABLE database_name.table_name RENAME TO new_table_name;
ALTER TABLE database_name.table_name ADD COLUMN column_def...;