创建复合主键：create table mapping(adminId integer,roleId integer,primary key(adminId,roleId)); @H_502_0@ @H_502_0@ 这样我的两个字段就都成为主键了。 @H_502_0@ @H_502_0@ 创建符合主键的同时建立外键： @H_502_0@ @H_502_0@ myd=# create table mapping(adminId integer references admin(id),roleId integer references role(id),roleId)); @H_502_0@ @H_502_0@ 这样我的的两个字段既是主键的组成部分，又分别参照了别的表的字段。 @H_502_0@ @H_502_0@ 创建符合主键的同时建立外键并级联删除级联跟新： @H_502_0@ @H_502_0@ myd=# create table mapping(adminid integer references admin(id) on delete cascade on update cascade,roleid integer references role(id) on delete cascade on update cascade,primary key(adminid,roleid)); @H_502_0@ @H_502_0@ 下面是提示信息： @H_502_0@ NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "mapping_pkey" for table "mapping" @H_502_0@ CREATE TABLE @H_502_0@ @H_502_0@ 多表连接： @H_502_0@ myd=# select (admin.id,admin.name,role.name) from admin,mapping,role where admin.id=mapping.adminid and mapping.roleid=role.id; @H_502_0@ @H_502_0@ 多表连接同时指定列的别名： @H_502_0@ myd=# select admin.id as id,admin.name as name,role.name as role from admin,role where admin.id=mapping.adminid and mapping.roleid=role.id; @H_502_0@ @H_502_0@ 对已经存在的表添加主键： @H_502_0@ alter table t add primary key(id); @H_502_0@ 其中t为表明，id为要设置为主键的字段，注意，如果字段中有重复值，会创建失败。 @H_502_0@ @H_502_0@ distinct去重 @H_502_0@ select count(distinct col) from A; @H_502_0@ @H_502_0@ select count(1) from (select 1 from A group by col) alias; @H_502_0@ @H_502_0@ copy导入文件和导出文件： @H_502_0@ COPY 命令可以快速的导入数据到 Postgresql 中，文件格式类似CVS之类。适合批量导入数据，比 \i 和恢复数据表快。 @H_502_0@ @H_502_0@ 导出表数据到文件或 STDOUT ： @H_502_0@ @H_502_0@ COPY tablename [(column [,...])] @H_502_0@ TO {'filename' | STDOUT} @H_502_0@ [[WITH] @H_502_0@ [BINARY] @H_502_0@ [OIDS] @H_502_0@ [DELIMITER [AS] 'delimiter'] @H_502_0@ [NULL [AS] 'null string'] @H_502_0@ [CSV [HEADER] @H_502_0@ [QUOTE [AS] 'quote'] @H_502_0@ [ESCAPE [AS] 'escape'] @H_502_0@ [FORCE NOT NULL column [,...]] @H_502_0@ @H_502_0@ 导入文件或者 STDIN 到表中： @H_502_0@ @H_502_0@ COPY tablename [(column [,...])] @H_502_0@ FROM {'filename' | STDIN} @H_502_0@ [[WITH] @H_502_0@ [BINARY] @H_502_0@ [OIDS] @H_502_0@ [DELIMITER [AS] 'delimiter'] @H_502_0@ [NULL [AS] 'null string'] @H_502_0@ [CSV [HEADER] @H_502_0@ [QUOTE [AS] 'quote'] @H_502_0@ [ESCAPE [AS] 'escape'] @H_502_0@ [FORCE QUOTE column [,...]] @H_502_0@ @H_502_0@ 导出表 employee 到默认输出 STDOUT： @H_502_0@ @H_502_0@ psql> COPY employee TO STDOUT; @H_502_0@ 1 JG100011 Jason Gilmore jason@example.com @H_502_0@ 2 RT435234 Robert Treat rob@example.com @H_502_0@ 3 GS998909 Greg Sabino Mullane greg@example.com @H_502_0@ 4 MW777983 Matt Wade matt@example.com @H_502_0@ @H_502_0@ 导出表 employee 到 sql 文件： @H_502_0@ @H_502_0@ psql> COPY employee TO '/home/smallfish/employee.sql'; @H_502_0@ @H_502_0@ 从文件导入数据： @H_502_0@ @H_502_0@ psql> COPY employeenew FROM '/home/smallfish/employee.sql'; @H_502_0@ psql> SELECT * FROM employeenew; @H_502_0@ employeeid | employeecode | name | email @H_502_0@ ------------+--------------+---------------------+--------------- @H_502_0@ 1 | JG100011 | Jason Gilmore | jason@example.com @H_502_0@ 2 | RT435234 | Robert Treat | rob@example.com @H_502_0@ 3 | GS998909 | Greg Sabino Mullane | greg@example.com @H_502_0@ 4 | MW777983 | Matt Wade | matt@example.com @H_502_0@ (4 rows) @H_502_0@ @H_502_0@ 输出对象ID（OIDS）： @H_502_0@ @H_502_0@ psql> COPY employee TO STDOUT OIDS; @H_502_0@ 24627 1 GM100011 Jason Gilmore jason@example.com @H_502_0@ 24628 2 RT435234 Robert Treat rob@example.com @H_502_0@ 24629 3 GS998909 Greg Sabino Mullane greg@example.com @H_502_0@ 24630 4 MW777983 Matt Wade matt@example.com @H_502_0@ @H_502_0@ 指定导出间隔符，默认是 \t ，这里为 | ： @H_502_0@ @H_502_0@ psql>COPY employee TO STDOUT DELIMITER '|'; @H_502_0@ 1|GM100011|Jason Gilmore|jason@example.com @H_502_0@ 2|RT435234|Robert Treat|rob@example.com @H_502_0@ 3|GS998909|Greg Sabino Mullane|greg@example.com @H_502_0@ 4|MW777983|Matt Wade|matt@example.com @H_502_0@ @H_502_0@ 导入文件数据，指定间隔符为 | ： @H_502_0@ @H_502_0@ psql> COPY employeenew FROM '/home/smallfish/employee.sql' DELIMITER |; @H_502_0@ @H_502_0@ 导出指定字段的数据： @H_502_0@ @H_502_0@ psql> COPY employee (name,email) TO STDOUT; @H_502_0@ Jason Gilmore jason@example.com @H_502_0@ Robert Treat rob@example.com @H_502_0@ Greg Sabino Mullane greg@example.com @H_502_0@ Matt Wade matt@example.com @H_502_0@ @H_502_0@ 为 NULL 字段设置默认值： @H_502_0@ @H_502_0@ psql> COPY employee TO STDOUT NULL 'no email'; @H_502_0@ Jason Gilmore no email @H_502_0@ Robert Treat rob@example.com @H_502_0@ Greg Sabino Mullane greg@example.com @H_502_0@ Matt Wade no email @H_502_0@ @H_502_0@ 导出为CVS格式： @H_502_0@ @H_502_0@ psql> COPY employee (name,email) TO '/home/smallfish/employee.csv' CSV HEADER; @H_502_0@

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MysqL导出数据到文件： select *(或者字段名) from tablename into outfile "/root/aa.txt";

MysqL导入到MysqL中： load data infile "/root/aa.txt" into table tablename; table需要提前创建好。

MySQL INTO OUTFILE/INFILE导出导入数据

--使用SELECT ... INTO OUTFILE 以逗号分隔字段的方式将数据导入到一个文件中:

--将刚刚导出的文件log1.txt导入到表log1相同结构的log2中:

-- 使用select * into outfile 导出:

-- 导入

FIELDS TERMINATED BY','字段间分割符 OPTIONALLY ENCLOSED BY'"'将字段包围 对数值型无效 LINES TERMINATED BY'\n'换行符