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表1：person
mysql>create database person;
mysql>CREATE TABLE IF NOT EXISTS `person_tbl`(
`person_id` INT UNSIGNED AUTO_INCREMENT,
`person_firstname` VARCHAR(100) NOT NULL,
`person_lastname` VARCHAR(40) NOT NULL,
PRIMARY KEY ( `person_id` )
)ENGINE=InnoDB DEFAULT CHARSET=utf8;
表2：address
mysql>create database address;
mysql>CREATE TABLE IF NOT EXISTS `address_tbl`(
`address_addressid` INT UNSIGNED AUTO_INCREMENT,
`address_personid` INT UNSIGNED AUTO_INCREMENT,
`address_city` VARCHAR(100) NOT NULL,
`address_state` VARCHAR(40) NOT NULL,
PRIMARY KEY ( `address_addressid` )
)ENGINE=InnoDB DEFAULT CHARSET=utf8;
SQL查询1：
mysql>SELECT person_firstname , person_lastname , address_city , address_state FROM address_tbl LEFT JOIN person_tbl;
SQL查询2：
mysql>create database person;
mysql>CREATE TABLE IF NOT EXISTS `person_tbl`(
`person_id` INT UNSIGNED AUTO_INCREMENT,
`person_email` VARCHAR(100) NOT NULL,
PRIMARY KEY ( `person_id` )
)ENGINE=InnoDB DEFAULT CHARSET=utf8;
mysql>select person_email from person group by person_email having count(person_email)>1;
总结：表的操作类似于集合的交并补，明确操作的对象，比如做inner join，就要明确哪些原来的表有，哪些没有，有没有是在合并操作时补充的。感觉用mysql的命令行还是有点不习惯，有语法错误出现时无法第一时间发现，在运行时才被报错，重打一遍又有点麻烦，或许可以试试PHP？
