MySQL 系统表列注释的应用

通过完整规范的列注释快速生成中文列名的SQL语句及数据字典。利用列注释可以减少表关联映射及联表查询，充分利用系统资源，简洁、高效。而其基础仅是一个列的注释规范。

一、用系统表元数据快速生成中文列名的SQL语句。

#1.建表
drop   table if exists t_01;
create table           t_01
(id int auto_increment comment 'ID',part_id tinyint       comment '部门ID 0:总经办;1:办公室;2:设计部;3:生产部;4:仓储部;5:财务部;6:后勤部;7:采购部;8:销售部;9:保安部;',name varchar(10)      comment '姓名',sex tinyint           comment '性别 0:女;1:男;2:不详;',dt_birth date         comment '生日',post int              comment  '职位代码 0:总经理;1:副总经理;2:经理;3:副经理;4:处长;4:副处长;5:科长;6:副科长;',salary nemberic(12,2) comment '薪资',bonus  nemberic(12,2) comment '奖金',primary key(id)
) comment '员工信息表';

#2.清空表
truncate table t_01;

#3.插入测试数据
insert into t_01(id,part_id,name,sex,dt_birth,post,salary,bonus) values
(1,0,'name_01',0,'2000-01-01',0,20001.00,2001.00),
(2,1,'name_02',1,'2000-01-02',0,20002.00,2002.00),
(3,0,'name_03',2,'2000-01-03',0,20003.00,2003.00),
(4,1,'name_04',3,'2000-01-04',0,20004.00,2004.00),
(5,0,'name_05',4,'2000-01-05',0,20005.00,2005.00),
(6,0,'name_06',5,'2000-01-06',0,20006.00,2006.00),
(7,0,'name_07',5,'2000-01-07',0,20007.00,2007.00),
(8,0,'name_08',5,'2000-01-08',0,20008.00,2008.00),
(9,0,'name_09',5,'2000-01-09',0,20009.00,2009.00),
(10,0,'name_10',5,'2000-01-10',0,20010.00,2010.00),
(11,0,'name_11',5,'2000-01-11',0,20011.00,2011.00),
(12,0,'name_12',5,'2000-01-12',0,20012.00,2012.00);

#4.查询
select * from t_01;

此时列名全是英文的。如果想把列名变成见名知意的中文，可以用中文列名做别名：

select id          '员工ID',part_id     '部门',name        '姓名',sex         '性别', dt_birth    '生日',post        '职位', education   '学历',salary      '薪资',bonus       '奖金'
from t_01;

每行中的数字所代表的意思还是不知其中文意思，要弄明白每列数字所表达的中文意思，必须用if 或case :

select id '员工ID',(case part_id when 0 then '总经办' when 1 then '办公室' when 2 then '设计部' when 3 then '生产部' when 4 then '仓储部' when 5 then '财务部' when 6 then '后勤部' when 7 then '采购部' when 8 then '销售部' when 9 then '保安部'else null end ) '部门',`name` '姓名',if(sex=0 ,'女', if(sex=1 ,'男',if(sex=2 ,'不详',''))) '性别', dt_birth '生日',(case post when 0  then '总经理' when 1 then '副总经理' when 2 then '经理' when 3 then '副经理' when 4 then '处长' when 4 then '副处长' when 5 then '科长' when 6 then '副科长' else null end) '职位', (case education when 0 then '博士' when 1 then '硕士' when 2 then '本科' when 3 then '专科' when 4 then '高中' when 5 then '初中' when 6 then '小学' else null end)'学历',salary '薪资',bonus '奖金'
from t_01;

这样列名和表中的数字都变成了见名知意的中文了。但又把列名和表中数字给淹没了，不知表中原来的列名和数字。
将字段名和中文一起描述，将表中的数字和代表的中文意思一起描述：

select id 'id:员工ID',(case part_id when 0 then '0:总经办' when 1 then '1:办公室' when 2 then '2:设计部' when 3 then '3:生产部' when 4 then '4:仓储部' when 5 then '5:财务部' when 6 then '6:后勤部' when 7 then '7:采购部' when 8 then '8:销售部' when 9 then '9:保安部' else null end ) 'part_id:部门',`name` 'name:姓名',if(sex=0 ,'0:女', if(sex=1 ,'1:男',if(sex=2 ,'2:不详',''))) 'sex:性别', dt_birth 'dt_birth:生日',(case post when 0 then '0:总经理' when 1 then '1:副总经理'when 2 then '2:经理' when 3 then '3:副经理' when 4 then '4:处长' when 4 then '5:副处长' when 5 then '6:科长' when 6 then '7:副科长' else null end) 'post:职位', (case education when 0 then '0:博士' when 1 then '1:硕士' when 2 then '2:本科' when 3 then '3:专科' when 4 then '4:高中' when 5 then '5:初中' when 6 then '6:小学' else null end)'education:学历',    salary 'salary:薪资',bonus 'bonus:奖金'
from t_01;

这样手工输入这些代码很繁琐，利用系统表information_schema.columns的列注释字段column_comment可以高效构造出所需的SQL语句，实现灵活的中文列和表中数字中文意思的查询。
关键:定义列注释的规范要求：中文列名数字1:中文意思1;数字2:中文意思2;数字3:中文意思3;...数字n:中文意思n;

#创建构造SQL语句的存储过程
drop    procedure if exists `p_01`;
create  procedure           `p_01`(p_table_schema varchar(40),p_table_name varchar(40),p_type int,p_chinese int,p_alias varchar(4))
comment
'获取表的列名的中文名及列属性的中文含义 (英文列名+中文列名)长度<=64p_table_schema 数据库名p_table_name 表名p_type SQL语句样式类型 0:横式;1;纵式p_chinese 是否生成中文列名 0:仅英文列名;1:仅中文列名;2:英文列名+中文列名; 当仅中文列名时，若column_comment中无中文注释时，则用column_namep_alias 表的别名p_separator 列名与中文列名之间、数字与中文意思之间的分隔符(未用)
'
beginif p_type<0 or p_type>1 then select concat('SQL语句样式类型 0:横式;1;纵式。') message;
end if;if p_chinese<0 or p_chinese>2 then select concat('是否生成中文列名 0:仅英文列名;1:仅中文列名;2:英文列名+中文列名') message;end if;
if length(p_alias)<=0 or length(p_alias)>4 thenselect concat('表别名最大长度为4个字符') message;
end if;#删除所有的临时表drop temporary table if exists temp_01;drop temporary table if exists temp_02;drop temporary table if exists temp_03;drop temporary table if exists temp_04;drop temporary table if exists temp_07;drop temporary table if exists temp_06;drop temporary table if exists temp_05;create temporary table temp_01(table_schema varchar(100),table_name varchar(100),column_name varchar(100),title longtext);if p_chinese=0 then #仅英文列名insert into temp_01select table_schema,table_name,column_name,concat(p_alias,'.',column_name,' ','`',concat(p_alias,'.',column_name),'`') title from information_schema.columns where table_schema=p_table_schema and table_name=p_table_name  ;end if;if p_chinese=1 then #仅中文列名insert into temp_01select table_schema,table_name,column_name,concat(p_alias,'.',column_name,' ','`',concat(p_alias,'.',trim(SUBSTRING_INDEX(if(length(column_comment)<1,column_name,column_comment),' ',1))),'`') title from information_schema.columns where table_schema=p_table_schema and table_name=p_table_name  ;end if;if p_chinese=2 then #英文列名 +中文列名insert into temp_01select table_schema,table_name,column_name,concat(p_alias,'.',column_name,' ','`',concat(p_alias,'.',column_name,':',trim(SUBSTRING_INDEX(column_comment,' ',1))),'`') title from information_schema.columns where table_schema=p_table_schema and table_name=p_table_name  ;end if;-- select concat('select ',left(@col_name,char_length(@col_name)-0),' from `',p_table_schema,'`.`',p_table_name,'`;') select_sql;-- 1.获取空格后的字符串create temporary table temp_02select table_schema,table_name,column_name,substring_index(column_comment,' ',1) column_comment,mid(column_comment,locate(' ',column_comment)+1) col7 from information_schema.columns where table_schema=p_table_schema and table_name=p_table_name and column_comment like '%;%';-- 2.按分号分隔后再按冒号分隔后转为列(横转纵)写入表中-- (1) 按分号分隔set @s=';';create temporary table temp_03select table_schema,table_name,column_name,column_comment,trim(substring_index(substring_index(a.`col7`, @s, b.help_topic_id + 1 ), @s,- 1 )) `col7`             from temp_02 ajoin mysql.help_topic b on b.help_topic_id < ( length( a.col7 ) - length( replace ( a.col7, @s, '' ) ) + 1 ) ;delete from temp_03 where col7=''; -- 删除多余的空数据-- (2) 按冒号分隔create temporary table temp_04select table_schema,table_name,column_name,column_comment,left(col7,locate(':',col7)-1 ) sn,mid(col7,locate(':',col7)+1) zh from temp_03;-- 3:获取列属性的中文含义if p_chinese=0 then #仅英文列名create temporary table temp_05select table_schema,column_name,concat("(case ",p_alias,'.',column_name," ",group_concat(concat("when ",sn," then '",sn,":",zh,"'") separator " ")," end)"," `",p_alias,'.',column_name,"`") `whenthen` from temp_04 group by table_schema,column_name,column_comment ;end if;if p_chinese=1 then #仅中文列名create temporary table temp_05select table_schema,column_name,concat("(case ",p_alias,'.',column_name," ",group_concat(concat("when ",sn," then '",sn,":",zh,"'") separator " ")," end)"," `",p_alias,'.',if(length(column_comment)<1,column_name,column_comment),"`") `whenthen` from temp_04 group by table_schema,column_name,column_comment ;end if;    if p_chinese=2 then #英文 +中文列名create temporary table temp_05select table_schema,column_name,concat("(case ",p_alias,'.',column_name," ",group_concat(concat("when ",sn," then '",sn,":",zh,"'") separator " ")," end)"," `",p_alias,'.',column_name,":",column_comment,"`") `whenthen` from temp_04 group by table_schema,column_name,column_comment ;end if;update temp_01 a,temp_05 b set a.title = b.whenthen  where  a.column_name =b.column_name and a.table_schema=b.table_schema;-- select * from temp_01 ;-- 纵转横-- 最终生成中文列名及中文属性值的 sql(横向)if p_type=0 then select concat('select ',group_concat(title separator ','),' from ',table_schema,'.',table_name, ' ',p_alias,' where 1=1 limit 10;') `sql` from temp_01 group by table_name;end if;if p_type=1 then -- 最终生成中文列名及中文属性值的 sql(纵向)create temporary table temp_06(col longtext);insert into temp_06select concat('select\n',concat('\t',group_concat(concat('\t',title) separator ',')),' \nfrom\n\t ',table_schema,'.',table_name,' ',p_alias,' \nwhere\n\t 1=1 limit 10;') `col`  from temp_01 group by table_name;set @s=',';create temporary table temp_07select concat(' ',trim(substring_index(substring_index(col, @s, b.help_topic_id + 1 ), @s,-1 )),',') `cmd` from temp_06 ajoin mysql.help_topic b on b.help_topic_id < ( length( a.col ) - length( replace ( a.col, @s, '' ) ) + 1 );-- 将最后一行的;,替换为;update temp_07 set cmd=replace(cmd,';,',';');-- 查询构造的SQL语句select cmd from temp_07;end if;
end;

select * from t_01;

#执行存储过程将生成SQL语句。

set @db='db_01',@tab='t_01',@type=0,@chinese=0,@alias='t1';call `db_01`.`p_01`(@db ,@tab,@type,@chinese,@alias);
set @db='db_01',@tab='t_01',@type=0,@chinese=1,@alias='t1';call `db_01`.`p_01`(@db ,@tab,@type,@chinese,@alias);
set @db='db_01',@tab='t_01',@type=0,@chinese=2,@alias='t1';call `db_01`.`p_01`(@db ,@tab,@type,@chinese,@alias);
set @db='db_01',@tab='t_01',@type=1,@chinese=0,@alias='t1';call `db_01`.`p_01`(@db ,@tab,@type,@chinese,@alias);
set @db='db_01',@tab='t_01',@type=1,@chinese=1,@alias='t1';call `db_01`.`p_01`(@db ,@tab,@type,@chinese,@alias);
set @db='db_01',@tab='t_01',@type=1,@chinese=2,@alias='t1';call `db_01`.`p_01`(@db ,@tab,@type,@chinese,@alias);

#生成的SQL语句：

select t1.id `t1.id`,(case t1.part_id when 0 then '0:总经办' when 1 then '1:办公室' when 2 then '2:设计部' when 3 then '3:生产部' when 4 then '4:仓储部' when 5 then '5:财务部' when 6 then '6:后勤部' when 7 then '7:采购部' when 8 then '8:销售部' when 9 then '9:保安部' end) `t1.part_id`,t1.name `t1.name`,(case t1.sex when 0 then '0:女' when 1 then '1:男' when 2 then '2:不详' end) `t1.sex`,t1.dt_birth `t1.dt_birth`,(case t1.education when 0 then '0:博士' when 1 then '1:硕士' when 2 then '2:本科' when 3 then '3:专科' when 4 then '4:高中' when 5 then '5:初中' when 6 then '6:小学' end) `t1.education`,(case t1.post when 0 then '0:总经理' when 1 then '1:副总经理' when 2 then '2:经理' when 3 then '3:副经理' when 4 then '4:处长' when 4 then '4:副处长' when 5 then '5:科长' when 6 then '6:副科长' end) `t1.post`,t1.salary `t1.salary`,t1.bonus `t1.bonus` from db_01.t_01 t1 where 1=1 limit 10;select t1.id `t1.ID`,(case t1.part_id when 0 then '0:总经办' when 1 then '1:办公室' when 2 then '2:设计部' when 3 then '3:生产部' when 4 then '4:仓储部' when 5 then '5:财务部' when 6 then '6:后勤部' when 7 then '7:采购部' when 8 then '8:销售部' when 9 then '9:保安部' end) `t1.部门ID`,t1.name `t1.姓名`,(case t1.sex when 0 then '0:女' when 1 then '1:男' when 2 then '2:不详' end) `t1.性别`,t1.dt_birth `t1.生日`,(case t1.education when 0 then '0:博士' when 1 then '1:硕士' when 2 then '2:本科' when 3 then '3:专科' when 4 then '4:高中' when 5 then '5:初中' when 6 then '6:小学' end) `t1.学历`,(case t1.post when 0 then '0:总经理' when 1 then '1:副总经理' when 2 then '2:经理' when 3 then '3:副经理' when 4 then '4:处长' when 4 then '4:副处长' when 5 then '5:科长' when 6 then '6:副科长' end) `t1.职位代码`,t1.salary `t1.薪资`,t1.bonus `t1.奖金` from db_01.t_01 t1 where 1=1 limit 10;select t1.id `t1.id:ID`,(case t1.part_id when 0 then '0:总经办' when 1 then '1:办公室' when 2 then '2:设计部' when 3 then '3:生产部' when 4 then '4:仓储部' when 5 then '5:财务部' when 6 then '6:后勤部' when 7 then '7:采购部' when 8 then '8:销售部' when 9 then '9:保安部' end) `t1.part_id:部门ID`,t1.name `t1.name:姓名`,(case t1.sex when 0 then '0:女' when 1 then '1:男' when 2 then '2:不详' end) `t1.sex:性别`,t1.dt_birth `t1.dt_birth:生日`,(case t1.education when 0 then '0:博士' when 1 then '1:硕士' when 2 then '2:本科' when 3 then '3:专科' when 4 then '4:高中' when 5 then '5:初中' when 6 then '6:小学' end) `t1.education:学历`,(case t1.post when 0 then '0:总经理' when 1 then '1:副总经理' when 2 then '2:经理' when 3 then '3:副经理' when 4 then '4:处长' when 4 then '4:副处长' when 5 then '5:科长' when 6 then '6:副科长' end) `t1.post:职位代码`,t1.salary `t1.salary:薪资`,t1.bonus `t1.bonus:奖金` from db_01.t_01 t1 where 1=1 limit 10;selectt1.id `t1.id`,(case t1.part_id when 0 then '0:总经办' when 1 then '1:办公室' when 2 then '2:设计部' when 3 then '3:生产部' when 4 then '4:仓储部' when 5 then '5:财务部' when 6 then '6:后勤部' when 7 then '7:采购部' when 8 then '8:销售部' when 9 then '9:保安部' end) `t1.part_id`,t1.name `t1.name`,(case t1.sex when 0 then '0:女' when 1 then '1:男' when 2 then '2:不详' end) `t1.sex`,t1.dt_birth `t1.dt_birth`,(case t1.education when 0 then '0:博士' when 1 then '1:硕士' when 2 then '2:本科' when 3 then '3:专科' when 4 then '4:高中' when 5 then '5:初中' when 6 then '6:小学' end) `t1.education`,(case t1.post when 0 then '0:总经理' when 1 then '1:副总经理' when 2 then '2:经理' when 3 then '3:副经理' when 4 then '4:处长' when 4 then '4:副处长' when 5 then '5:科长' when 6 then '6:副科长' end) `t1.post`,t1.salary `t1.salary`,t1.bonus `t1.bonus`
fromdb_01.t_01 t1
where1=1 limit 10;selectt1.id `t1.ID`,(case t1.part_id when 0 then '0:总经办' when 1 then '1:办公室' when 2 then '2:设计部' when 3 then '3:生产部' when 4 then '4:仓储部' when 5 then '5:财务部' when 6 then '6:后勤部' when 7 then '7:采购部' when 8 then '8:销售部' when 9 then '9:保安部' end) `t1.部门ID`,t1.name `t1.姓名`,(case t1.sex when 0 then '0:女' when 1 then '1:男' when 2 then '2:不详' end) `t1.性别`,t1.dt_birth `t1.生日`,(case t1.education when 0 then '0:博士' when 1 then '1:硕士' when 2 then '2:本科' when 3 then '3:专科' when 4 then '4:高中' when 5 then '5:初中' when 6 then '6:小学' end) `t1.学历`,(case t1.post when 0 then '0:总经理' when 1 then '1:副总经理' when 2 then '2:经理' when 3 then '3:副经理' when 4 then '4:处长' when 4 then '4:副处长' when 5 then '5:科长' when 6 then '6:副科长' end) `t1.职位代码`,t1.salary `t1.薪资`,t1.bonus `t1.奖金`
fromdb_01.t_01 t1
where1=1 limit 10;selectt1.id `t1.id:ID`,(case t1.part_id when 0 then '0:总经办' when 1 then '1:办公室' when 2 then '2:设计部' when 3 then '3:生产部' when 4 then '4:仓储部' when 5 then '5:财务部' when 6 then '6:后勤部' when 7 then '7:采购部' when 8 then '8:销售部' when 9 then '9:保安部' end) `t1.part_id:部门ID`,t1.name `t1.name:姓名`,(case t1.sex when 0 then '0:女' when 1 then '1:男' when 2 then '2:不详' end) `t1.sex:性别`,t1.dt_birth `t1.dt_birth:生日`,(case t1.education when 0 then '0:博士' when 1 then '1:硕士' when 2 then '2:本科' when 3 then '3:专科' when 4 then '4:高中' when 5 then '5:初中' when 6 then '6:小学' end) `t1.education:学历`,(case t1.post when 0 then '0:总经理' when 1 then '1:副总经理' when 2 then '2:经理' when 3 then '3:副经理' when 4 then '4:处长' when 4 then '4:副处长' when 5 then '5:科长' when 6 then '6:副科长' end) `t1.post:职位代码`,t1.salary `t1.salary:薪资`,t1.bonus `t1.bonus:奖金`
fromdb_01.t_01 t1
where1=1 limit 10;

#执行生成的SQL语句，可得到预期的结果样式(结果一样，只是列头样式不一样)。
英文列名

中文列名

英文+中文列名

二、用系统表元数据快速生成数据字典。

#生成数据字典
drop   procedure if exists p_02;
create procedure           p_02(p_table_schema varchar(40),p_table_name varchar(40),p_chinese tinyint)
comment
'生成数据字典p_table_schema 数据库名。为空或长度为0则为所有用户数据库;否则为指定的数据库。p_table_name 表名。为空或长库为0则为所有表。t_chinese 是否生成中文列名 0:仅英文列名;1:仅中文列名;2:英文列名+中文列名;9:显示存储过程用法帮助;
'
begindeclare v_ret int default 0;if p_chinese=9 then select '生成数据字典p_table_schema 数据库名。为空或长度为0则为所有用户数据库;否则为指定的数据库。p_table_name 表名。为空或长库为0则为所有表。t_chinese 是否生成中文列名 0:仅英文列名;1:仅中文列名;2:英文列名+中文列名;' messagefrom dual;end if;#所有数据库if p_table_schema is null or length(p_table_schema)=0 then#所有表if p_table_name is null or length(p_table_name)=0 then#0:仅英文列名if p_chinese =0 then select table_schema ,table_name ,column_name ,column_default ,is_nullable ,data_type ,column_type,column_key ,extra ,column_comment from information_schema.columnsorder by table_schema,table_name;end if;#1:仅中文列名if p_chinese=1 thenselect table_schema `数据库名`,table_name `表名`,column_name `列名`,column_default `缺省值`,is_nullable `是否允许为空`,data_type `数据类型`,column_type`列类型`,column_key`主键`,extra `特别`,column_comment `列注释` from information_schema.columnsorder by table_schema,table_name;end if;#英文列名+中文列名if p_chinese=2 thenselect table_schema `table_schema:数据库名`,table_name `table_name:表名`,column_name `column_name:列名`,column_default `column_default:缺省值`,is_nullable `is_nullable:是否允许为空`,data_type `data_type:数据类型`,column_type`column_type:列类型`,column_key`column_key:主键`,extra `extra:特别`,column_comment `column_comment:列注释` from information_schema.columnsorder by table_schema,table_name;end if; #指定表elseselect count(*) into v_ret from information_schema.tables where table_name=p_table_name;if v_ret <=0 thenselect concat('无此表名: ',p_table_name,' !') message;else#0:仅英文列名if p_chinese=0 thenselect table_schema ,table_name ,column_name ,column_default ,is_nullable ,data_type ,column_type,column_key ,extra ,column_comment  from information_schema.columns where table_name=p_table_nameorder by table_schema,table_name;end if;#1:仅中文列名if p_chinese=1 thenselect table_schema `数据库名`,table_name `表名`,column_name `列名`,column_default `缺省值`,is_nullable `是否允许为空`,data_type `数据类型`,column_type`列类型`,column_key`主键`,extra `特别`,column_comment `列注释`  from information_schema.columns where table_name=p_table_nameorder by table_schema,table_name;end if;#英文列名+中文列名if p_chinese=2 thenselect table_schema `table_schema:数据库名`,table_name `table_name:表名`,column_name `column_name:列名`,column_default `column_default:缺省值`,is_nullable `is_nullable:是否允许为空`,data_type `data_type:数据类型`,column_type`column_type:列类型`,column_key`column_key:主键`,extra `extra:特别`,column_comment `column_comment:列注释` from information_schema.columns where table_name=p_table_nameorder by table_schema,table_name;end if;end if;end if;#指定数据库elseselect count(*) into v_ret from information_schema.tables where table_schema=p_table_schema;if v_ret<=0 then select concat('无此数据库名: ',p_table_schema,' !') message;else#所有表if p_table_name is null or length(p_table_name)=0 then#0:仅英文列名if p_chinese=0 thenselect table_schema ,table_name ,column_name ,column_default ,is_nullable ,data_type ,column_type,column_key ,extra ,column_comment from information_schema.columns where lower(table_schema)=p_table_schemaorder by table_schema,table_name;end if;#1:仅中文列名if p_chinese=1 thenselect table_schema `数据库名`,table_name `表名`,column_name `列名`,column_default `缺省值`,is_nullable `是否允许为空`,data_type `数据类型`,column_type`列类型`,column_key`主键`,extra `特别`,column_comment `列注释`  from information_schema.columns where lower(table_schema)=p_table_schemaorder by table_schema,table_name;end if;#英文列名+中文列名if p_chinese=2 thenselect table_schema `table_schema:数据库名`,table_name `table_name:表名`,column_name `column_name:列名`,column_default `column_default:缺省值`,is_nullable `is_nullable:是否允许为空`,data_type `data_type:数据类型`,column_type`column_type:列类型`,column_key`column_key:主键`,extra `extra:特别`,column_comment `column_comment:列注释` from information_schema.columns where lower(table_schema)=p_table_schemaorder by table_schema,table_name;end if;#指定表elseselect count(*) into v_ret from information_schema.tables where table_schema=p_table_schema and table_name=p_table_name;if v_ret <=0 thenselect concat('无此表名: ',p_table_name,' !') message;else#0:仅英文列名if p_chinese=0 thenselect table_schema ,table_name ,column_name ,column_default ,is_nullable ,data_type ,column_type,column_key ,extra ,column_comment  from information_schema.columns where lower(table_schema)=p_table_schema and table_name=p_table_nameorder by table_schema,table_name;end if;#1:仅中文列名if p_chinese=1 thenselect table_schema `数据库名`,table_name `表名`,column_name `列名`,column_default `缺省值`,is_nullable `是否允许为空`,data_type `数据类型`,column_type`列类型`,column_key`主键`,extra `特别`,column_comment `列注释`from information_schema.columns where lower(table_schema)=p_table_schema and table_name=p_table_nameorder by table_schema,table_name;end if;#英文列名+中文列名if p_chinese=2 thenselect table_schema `table_schema:数据库名`,table_name `table_name:表名`,column_name `column_name:列名`,column_default `column_default:缺省值`,is_nullable `is_nullable:是否允许为空`,data_type `data_type:数据类型`,column_type`column_type:列类型`,column_key`column_key:主键`,extra `extra:特别`,column_comment `column_comment:列注释` from information_schema.columns where lower(table_schema)=p_table_schema and table_name=p_table_nameorder by table_schema,table_name;end if;end if;end if;end if;end if;
end;

#执行存储过程将生成相应数据库对象的数据字典(含系统数据库及系统表)。

set @db='',@tab='',@chinese=0;call p_02(@db,@tab,@chinese);
set @db='',@tab='',@chinese=1;call p_02(@db,@tab,@chinese);
set @db='',@tab='',@chinese=2;call p_02(@db,@tab,@chinese);set @db='',@tab='t_01',@chinese=0;call p_02(@db,@tab,@chinese);
set @db='',@tab='t_01',@chinese=1;call p_02(@db,@tab,@chinese);
set @db='',@tab='t_01',@chinese=2;call p_02(@db,@tab,@chinese);set @db='db_01',@tab='',@chinese=0;call p_02(@db,@tab,@chinese);
set @db='db_01',@tab='',@chinese=1;call p_02(@db,@tab,@chinese);
set @db='db_01',@tab='',@chinese=2;call p_02(@db,@tab,@chinese);set @db='db_01',@tab='t_01',@chinese=0;call p_02(@db,@tab,@chinese);
set @db='db_01',@tab='t_01',@chinese=1;call p_02(@db,@tab,@chinese);
set @db='db_01',@tab='t_01',@chinese=2;call p_02(@db,@tab,@chinese);

三、用函数封装case 或 if 语句。

select id '员工ID',(case part_id when 0 then '总经办' when 1 then '办公室' when 2 then '设计部' when 3 then '生产部' when 4 then '仓储部' when 5 then '财务部' when 6 then '后勤部' when 7 then '采购部' when 8 then '销售部' when 9 then '保安部'else null end ) '部门',`name` '姓名',if(sex=0 ,'女', if(sex=1 ,'男',if(sex=2 ,'不详',''))) '性别', dt_birth '生日',(case post when 0  then '总经理' when 1 then '副总经理' when 2 then '经理' when 3 then '副经理' when 4 then '处长' when 4 then '副处长' when 5 then '科长' when 6 then '副科长' else null end) '职位', (case education when 0 then '博士' when 1 then '硕士' when 2 then '本科' when 3 then '专科' when 4 then '高中' when 5 then '初中' when 6 then '小学' else null end)'学历',salary '薪资',bonus '奖金'
from t_01;

这段简单的SQL语句里有多个的case和if 子句,复杂的SQL语句可能会更多这样的case 和if 子句。
将其中的case 用函数封装，可以统一固化数字所表达的中文语义、令SQL语句简洁，逻辑清晰，且可被所有成员共享调用。

#根据part_id返回部门名称
drop   function if exists f_01;
create function           f_01(p_part_id int) returns varchar(100)
comment '根据part_id返回部门名称'
begindeclare v_ret varchar(100) default '';select (   case p_part_id when 0 then '总经办'when 1 then '办公室'   when 2 then '设计部' when 3 then '生产部' when 4 then '仓储部' when 5 then '财务部' when 6 then '后勤部' when 7 then '采购部' when 8 then '销售部'when 9 then '保安部' else null end) into v_ret;return(v_ret);
end;


#根据post返回职位
drop   function if exists f_02;
create function           f_02(p_post int) returns varchar(100)
comment '根据post返回职位'
begindeclare v_ret varchar(100) default '';select (case p_post when 0 then'总经理' when 1 then'副总经理' when 2 then'经理' when 3 then'副经理' when 4 then'处长' when 5 then'副处长' when 6 then'科长' when 7 then'副科长' else null end )  into v_ret;
return(v_ret);
end;


#根据education返回学历
drop   function if exists f_03;
create function           f_03(p_education int) returns varchar(100)
comment '根据education返回学历'
begindeclare v_ret varchar(100) default '';select (case p_education when 0 then'博士' when 1 then'硕士' when 2 then'本科' when 3 then'专科' when 4 then '高中' when 5 then '初中' when 6 then '小学' else null end) into v_ret;return(v_ret);
end;

#根据sex返回性别
drop   function if exists f_04;
create function           f_04(p_sex int) returns varchar(100)
comment '根据sex返回部门性别'
begindeclare v_ret varchar(100) default '';select if(p_sex=0,'女',if(p_sex=1,'男',if(p_sex=2,'不详',''))) into v_ret;return(v_ret);
end;

再用函数来执行之前的SQL语句，清爽简洁。

select id                 '员工ID',f_01(part_id)      '部门',`name`             '姓名',f_04(sex)          '性别', dt_birth           '生日',f_02(post)         '职位', f_03(education)    '学历',salary             '薪资',bonus              '奖金'
from t_01;

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