博主依然不想打字，又向你仍来了一堆代码。。。
13（续）
在SELECT中用COUNT（）以及联合
mysql> SELECT customers.cust_id,COUNT(orders.order_num) AS num_ord
-> FROM customers INNER JOIN orders
-> ON customers.cust_id=orders.cust_id
-> GROUP BY cust_id;
+------------+---------+
| cust_id | num_ord |
+------------+---------+
| 1000000001 | 2 |
| 1000000003 | 1 |
| 1000000004 | 1 |
| 1000000005 | 1 |
+------------+---------+
4 rows in set (0.00 sec)
14、组合查询
UNION，UNION ALL（显示重复行）；
多条SELECT合并为一个查询输出；
必须有相同的列数，顺序可以不一样但数据类型要可以转换的；
UNION ALL显示重复行，除此以外的使用，都可以用WHERE来替换；
ORDER BY放在最后一句，只需要一句；
不过事实证明，顺序还是会有影响的 。。。
mysql> SELECT cust_name,cust_contact,cust_emali
-> FROM customers
-> WHERE cust_state IN ('IL','IN','MI');
ERROR 1054 (42S22): Unknown column 'cust_emali' in 'field list'
mysql> SELECT cust_name,cust_contact,cust_email
-> FROM customers
-> WHERE cust_state IN ('IL','IN','MI');
+---------------+--------------+-----------------------+
| cust_name | cust_contact | cust_email |
+---------------+--------------+-----------------------+
| Village Toys | John Smith | sales@villagetoys.com |
| Fun4All | Jim Jones | jjones@fun4all.com |
| The Toy Store | Kim Howard | NULL |
+---------------+--------------+-----------------------+
3 rows in set (0.00 sec)mysql> SELECT cust_name,cust_email,cust_contact
-> FROM customers
-> WHERE cust_name='Fun4All';
+-----------+-----------------------+--------------------+
| cust_name | cust_email | cust_contact |
+-----------+-----------------------+--------------------+
| Fun4All | jjones@fun4all.com | Jim Jones |
| Fun4All | dstephens@fun4all.com | Denise L. Stephens |
+-----------+-----------------------+--------------------+
2 rows in set (0.00 sec)mysql> SELECT cust_name,cust_contact,cust_email
-> FROM customers
-> WHERE cust_state IN ('IL','IN','MI')
-> UNION
-> SELECT cust_name,cust_email,cust_contact
-> FROM customers
-> WHERE cust_name='Fun4All';
+---------------+-----------------------+-----------------------+
| cust_name | cust_contact | cust_email |
+---------------+-----------------------+-----------------------+
| Village Toys | John Smith | sales@villagetoys.com |
| Fun4All | Jim Jones | jjones@fun4all.com |
| The Toy Store | Kim Howard | NULL |
| Fun4All | jjones@fun4all.com | Jim Jones |
| Fun4All | dstephens@fun4all.com | Denise L. Stephens |
+---------------+-----------------------+-----------------------+
5 rows in set (0.00 sec)mysql> SELECT cust_name,cust_contact,cust_email
-> FROM customers
-> WHERE cust_state IN ('IL','IN','MI')
-> UNION
-> SELECT cust_name,cust_contact,cust_email
-> FROM customers
-> WHERE cust_name='Fun4All';
+---------------+--------------------+-----------------------+
| cust_name | cust_contact | cust_email |
+---------------+--------------------+-----------------------+
| Village Toys | John Smith | sales@villagetoys.com |
| Fun4All | Jim Jones | jjones@fun4all.com |
| The Toy Store | Kim Howard | NULL |
| Fun4All | Denise L. Stephens | dstephens@fun4all.com |
+---------------+--------------------+-----------------------+
4 rows in set (0.00 sec)mysql> SELECT cust_name,cust_contact,cust_email
-> FROM customers
-> WHERE cust_state IN ('IL','IN','MI')
-> UNION ALL
-> SELECT cust_name,cust_contact,cust_email
-> FROM customers
-> WHERE cust_name='Fun4All';
+---------------+--------------------+-----------------------+
| cust_name | cust_contact | cust_email |
+---------------+--------------------+-----------------------+
| Village Toys | John Smith | sales@villagetoys.com |
| Fun4All | Jim Jones | jjones@fun4all.com |
| The Toy Store | Kim Howard | NULL |
| Fun4All | Jim Jones | jjones@fun4all.com |
| Fun4All | Denise L. Stephens | dstephens@fun4all.com |
+---------------+--------------------+-----------------------+
5 rows in set (0.00 sec)mysql> SELECT cust_name,cust_contact,cust_email
-> FROM customers
-> WHERE cust_state IN ('IL','IN','MI')
-> UNION
-> SELECT cust_name,cust_contact,cust_email
-> FROM customers
-> WHERE cust_name='Fun4All'
-> ORDER BY cust_name;
+---------------+--------------------+-----------------------+
| cust_name | cust_contact | cust_email |
+---------------+--------------------+-----------------------+
| Fun4All | Jim Jones | jjones@fun4all.com |
| Fun4All | Denise L. Stephens | dstephens@fun4all.com |
| The Toy Store | Kim Howard | NULL |
| Village Toys | John Smith | sales@villagetoys.com |
+---------------+--------------------+-----------------------+
4 rows in set (0.00 sec)
15、插入数据
INSERT,INSERT INTO,INSERT SELECT,SELECT INTO
插入完整的行，插入行的一部分，插入某些查询结果；
用INSERT INTO替代INSERT，提高可移植性；
注意格式写法；
最好写上列名；
INSERT一般只能插入一条，INSERT SELECT是个例外；
SELECT INTO实现复制（MySQL和Oracle的有所不同）
mysql> CREATE TABLE custNew(
-> cust_id INT PRIMARY KEY,
-> cust_contact VARCHAR(32),
-> cust_email VARCHAR(32),
-> cust_name VARCHAR(32),
-> cust_address VARCHAR(64),
-> cust_city VARCHAR(16),
-> cust_state VARCHAR(16),
-> cust_zip SMALLINT,
-> cust_country VARCHAR(16)
-> );
Query OK, 0 rows affected (0.21 sec)mysql> INSERT INTO custNew(
-> cust_id,
-> cust_email,
-> cust_name,
-> cust_zip,
-> cust_country,
-> cust_city)
-> VALUES(
-> 1021,
-> 'liangbocv@126.com',
-> 'Andy Liang',
-> 610000,
-> 'China',
-> 'Chengdu');
Query OK, 1 row affected, 1 warning (0.04 sec)mysql> INSERT INTO customers(
-> cust_id,
-> cust_email,
-> cust_name,
-> cust_zip,
-> cust_country,
-> cust_city)
-> SELECT cust_id,
-> cust_email,
-> cust_name,
-> cust_zip,
-> cust_country,
-> cust_city
-> FROM custNew;
Query OK, 1 row affected (0.03 sec)
Records: 1 Duplicates: 0 Warnings: 0mysql> SELECT * FROM customers;
+------------+---------------+----------------------+-----------+------------+----------+--------------+--------------------+-----------------------+
| cust_id | cust_name | cust_address | cust_city | cust_state | cust_zip | cust_country | cust_contact | cust_email |
+------------+---------------+----------------------+-----------+------------+----------+--------------+--------------------+-----------------------+
| 1000000001 | Village Toys | 200 Maple Lane | Detroit | MI | 44444 | USA | John Smith | sales@villagetoys.com |
| 1000000002 | Kids Place | 333 South Lake Drive | Columbus | OH | 43333 | USA | Michelle Green | NULL |
| 1000000003 | Fun4All | 1 Sunny Place | Muncie | IN | 42222 | USA | Jim Jones | jjones@fun4all.com |
| 1000000004 | Fun4All | 829 Riverside Drive | Phoenix | AZ | 88888 | USA | Denise L. Stephens | dstephens@fun4all.com |
| 1000000005 | The Toy Store | 4545 53rd Street | Chicago | IL | 54545 | USA | Kim Howard | NULL |
| 1021 | Andy Liang | NULL | Chengdu | NULL | 32767 | China | NULL | liangbocv@126.com |
+------------+---------------+----------------------+-----------+------------+----------+--------------+--------------------+-----------------------+
6 rows in set (0.00 sec)mysql> CREATE TABLE custcopy(
-> cust_id VARCHAR(16),
-> cust_contact VARCHAR(32),
-> cust_email VARCHAR(32),
-> cust_name VARCHAR(32),
-> cust_address VARCHAR(64),
-> cust_city VARCHAR(16),
-> cust_state VARCHAR(16),
-> cust_zip VARCHAR(16),
-> cust_country VARCHAR(16)
-> );
Query OK, 0 rows affected (0.26 sec)mysql> SELECT *
-> INTO custcopy
-> FROM customers;
ERROR 1327 (42000): Undeclared variable: custcopy
mysql> CREATE TABLE custcopy2 AS
-> SELECT *
-> FROM customers;
Query OK, 6 rows affected (0.41 sec)
Records: 6 Duplicates: 0 Warnings: 0
16、更新和删除数据
UPADTE,DELETE
容易使用，但请小心使用；（没有UNDO！！！）
UPDATE为null=DELETE；
一些习惯：一定带WHERE ,避免对整个表有影响；
对数据做更改时，请先SELECT查询一下，看对象是否没错；
确保每个表有主键
mysql> SELECT cust_id,cust_address,cust_state
-> FROM customers
-> WHERE cust_id='';
+---------+--------------+------------+
| cust_id | cust_address | cust_state |
+---------+--------------+------------+
| 1021 | NULL | NULL |
+---------+--------------+------------+
1 row in set (0.00 sec)mysql> UPDATE customers
-> SET cust_address='2006 Xiyuan Ave.',
-> cust_state='SC'
-> WHERE cust_id='';
Query OK, 1 row affected (0.02 sec)
Rows matched: 1 Changed: 1 Warnings: 0mysql> SELECT cust_id,cust_address,cust_state
-> FROM customers
-> WHERE cust_id='';
+---------+------------------+------------+
| cust_id | cust_address | cust_state |
+---------+------------------+------------+
| 1021 | 2006 Xiyuan Ave. | SC |
+---------+------------------+------------+
1 row in set (0.00 sec)mysql> UPDATE customers
-> SET cust_email=NULL
-> WHERE cust_id='';
Query OK, 1 row affected (0.03 sec)
Rows matched: 1 Changed: 1 Warnings: 0mysql> DELETE FROM customers
-> WHERE cust_id='';
Query OK, 1 row affected (0.08 sec)
17、创建和操作表
CREATE,DROP,ALTER,RENAME,DEFAULT
更新表，和更新数据一样小心，做好备份；
重命名不太一样，mysql是RENAME
mysql> ALTER TABLE custcopy2
-> ADD cust_gender VARCHAR(8);
Query OK, 0 rows affected (0.41 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> SELECT CURRENT_DATE();
+----------------+
| CURRENT_DATE() |
+----------------+
| 2016-08-10 |
+----------------+
1 row in set (0.16 sec)mysql> ALTER TABLE custcopy2
-> ADD add_time TIMESTAMP DEFAULT CURRENT_TIMESTAMP;
Query OK, 0 rows affected (0.46 sec)
Records: 0 Duplicates: 0 Warnings: 0mysql> DROP TABLE custcopy;
Query OK, 0 rows affected (0.13 sec)mysql> RENAME TABLE custcopy2 TO custcopy;
Query OK, 0 rows affected (0.10 sec)
18、使用视图
VIEW
view实际上就是个虚拟的表，只包含使用时动态检索数据的查询；
使用view，有利于代码重用，保护数据，简化操作；
视图名也要唯一；可以嵌套，一般禁止ORDER BY；
用于简化复杂联结，格式化输出，过滤不想要的数据等；
WHERE语句会自动合并
mysql> CREATE VIEW shit AS
-> SELECT cust_name,cust_id,cust_contact,cust_address
-> FROM customers
-> ;
Query OK, 0 rows affected (0.07 sec)mysql> SELECT cust_name,cust_address
-> FROM shit
-> WHERE cust_id='';
Empty set (0.00 sec)mysql> SELECT * FROM customers;
+------------+---------------+----------------------+-----------+------------+----------+--------------+--------------------+-----------------------+
| cust_id | cust_name | cust_address | cust_city | cust_state | cust_zip | cust_country | cust_contact | cust_email |
+------------+---------------+----------------------+-----------+------------+----------+--------------+--------------------+-----------------------+
| 1000000001 | Village Toys | 200 Maple Lane | Detroit | MI | 44444 | USA | John Smith | sales@villagetoys.com |
| 1000000002 | Kids Place | 333 South Lake Drive | Columbus | OH | 43333 | USA | Michelle Green | NULL |
| 1000000003 | Fun4All | 1 Sunny Place | Muncie | IN | 42222 | USA | Jim Jones | jjones@fun4all.com |
| 1000000004 | Fun4All | 829 Riverside Drive | Phoenix | AZ | 88888 | USA | Denise L. Stephens | dstephens@fun4all.com |
| 1000000005 | The Toy Store | 4545 53rd Street | Chicago | IL | 54545 | USA | Kim Howard | NULL |
+------------+---------------+----------------------+-----------+------------+----------+--------------+--------------------+-----------------------+
5 rows in set (0.00 sec)mysql> SELECT cust_name,cust_address
-> FROM shit
-> WHERE cust_id='';
+--------------+----------------+
| cust_name | cust_address |
+--------------+----------------+
| Village Toys | 200 Maple Lane |
+--------------+----------------+
1 row in set (0.00 sec)mysql> CREATE VIEW hasEmail AS
-> SELECT cust_name,cust_id,cust_email
-> FROM customers
-> WHERE cust_email IS NOT NULL;
Query OK, 0 rows affected (0.06 sec)mysql> SELECT *
-> FROM hasEmail
-> WHERE cust_name='Fun4All';
+-----------+------------+-----------------------+
| cust_name | cust_id | cust_email |
+-----------+------------+-----------------------+
| Fun4All | 1000000003 | jjones@fun4all.com |
| Fun4All | 1000000004 | dstephens@fun4all.com |
+-----------+------------+-----------------------+
2 rows in set (0.00 sec)
19、存储过程
PROCEDURE,DELIMITER,CALL
以下引用自百度：存储过程（Stored Procedure）是在大型数据库系统中，一组为了完成特定功能的SQL 语句集，存储在数据库中，经过第一次编译后再次调用不需要再次编译，用户通过指定存储过程的名字并给出参数（如果该存储过程带有参数）来执行它。存储过程是数据库中的一个重要对象，任何一个设计良好的数据库应用程序都应该用到存储过程。
有点好玩又有点繁琐的。。。
mysql> DELIMITER &&
mysql> CREATE PROCEDURE showAll()
-> BEGIN
-> SELECT * FROM customers;
-> END &&
Query OK, 0 rows affected (0.04 sec)mysql> CALL showAll();
+------------+---------------+----------------------+-----------+------------+----------+--------------+--------------------+-----------------------+
| cust_id | cust_name | cust_address | cust_city | cust_state | cust_zip | cust_country | cust_contact | cust_email |
+------------+---------------+----------------------+-----------+------------+----------+--------------+--------------------+-----------------------+
| 1000000001 | Village Toys | 200 Maple Lane | Detroit | MI | 44444 | USA | John Smith | sales@villagetoys.com |
| 1000000002 | Kids Place | 333 South Lake Drive | Columbus | OH | 43333 | USA | Michelle Green | NULL |
| 1000000003 | Fun4All | 1 Sunny Place | Muncie | IN | 42222 | USA | Jim Jones | jjones@fun4all.com |
| 1000000004 | Fun4All | 829 Riverside Drive | Phoenix | AZ | 88888 | USA | Denise L. Stephens | dstephens@fun4all.com |
| 1000000005 | The Toy Store | 4545 53rd Street | Chicago | IL | 54545 | USA | Kim Howard | NULL |
+------------+---------------+----------------------+-----------+------------+----------+--------------+--------------------+-----------------------+
5 rows in set (0.00 sec)Query OK, 0 rows affected (0.08 sec)mysql> DELIMITER $
mysql> CREATE PROCEDURE getID(
-> IN id VARCHAR(32))
-> BEGIN
-> SELECT *
-> FROM customers
-> WHERE cust_id=id;
-> END $
Query OK, 0 rows affected (0.00 sec)mysql> CALL getID('')$
+------------+--------------+----------------+-----------+------------+----------+--------------+--------------+-----------------------+
| cust_id | cust_name | cust_address | cust_city | cust_state | cust_zip | cust_country | cust_contact | cust_email |
+------------+--------------+----------------+-----------+------------+----------+--------------+--------------+-----------------------+
| 1000000001 | Village Toys | 200 Maple Lane | Detroit | MI | 44444 | USA | John Smith | sales@villagetoys.com |
+------------+--------------+----------------+-----------+------------+----------+--------------+--------------+-----------------------+
1 row in set (0.00 sec)Query OK, 0 rows affected (0.03 sec)mysql> DELIMITER ;
注意输入参数那里的变化。
20、事务管理
TRANSACTION,COMMIT,ROLLBACK,SAVEPOINT
用来维护数据库的完整性，保证成批的SQL操作要么完全执行，要么完全不执行；
保留点越多越好，更好的是形成习惯~
mysql> BEGIN;
Query OK, 0 rows affected (0.00 sec)mysql> SAVEPOINT begin;
Query OK, 0 rows affected (0.00 sec)mysql> INSERT INTO customers(cust_name,cust_country)
-> VALUES('Andy Liang','China');
Query OK, 1 row affected, 1 warning (0.00 sec)mysql> ROLLBACK TO begin;
Query OK, 0 rows affected (0.04 sec)mysql> COMMIT;
Query OK, 0 rows affected (0.00 sec)
MySQL是一步步来的，就是慢慢监督的一样。
21、使用游标
CURSOR
略。。。。（老子做web不想用游标，你来打我啊
22、约束，索引，触发器
约束:
PRIMARY KEY,UNIQUE,REFERENCES,ALTER,CONSTRAINT,CHECK
主键：值互异，NOT NULL，不修改/更新，不重用，每个表仅能有一个主键，可以用来定义外键（举例：id
唯一：值互异，可以有NULL，可修改/更新，可重用，可有多个唯一键，不能用来定义外键
外键：两个表，确定子表某一列的合法性
检查约束：CHECK，灵活约束
mysql> CREATE TABLE test(
-> id SMALLINT NOT NULL PRIMARY KEY AUTO_INCREMENT,
-> socialid VARCHAR(64) UNIQUE,
-> cust_id VARCHAR(16) NOT NULL REFERENCES customers(cust_id),
-> quantity SMALLINT CHECK (quantity>0),
-> gender VARCHAR(8) CHECK (gender LIKE '[MF]')
-> );
Query OK, 0 rows affected (0.20 sec)
另外，用ALTER语句再对表进行更改操作
ALTER TABLE test
ADD CONSTRAINT PRIMARY KEY (cust_id);ALTER TABLE test
ADD CONSTRAINT UNIQUE KEY (id);ALTER TABLE test
ADD CONSTRAINT
FOREIGN KEY (cust_id) REFERENCES customers (cust_id);ALTER TABLE test
ADD CONSTRAINT CHECK (quantity<1000);
索引：
INDEX
搜索某些列的效率提高；
请动态的创建索引——数据库在不断更新，索引效率在变化；索引效率提升的代价是插入等操作性能的牺牲；大量空间的使用；
mysql> CREATE INDEX prod_name_id
-> ON PRODUCTS (prod_name);
Query OK, 0 rows affected (0.31 sec)
Records: 0 Duplicates: 0 Warnings: 0
触发器：
TRIGGER
在特定的数据库活动发生时自动执行；
一般用途：保证数据一致（全大写等），联动（log的记录）等；
约束要比触发器快，尽量用约束；
完！！（对，这里又灭有代码了
