Sql获取表所有列名字段——select * 替换写法，Sqlserver、Oracle、PostgreSQL、Mysql

实际开发中经常用到select * from table，往往需要知道具体的字段，这个时候再去数据库中翻或者查看数据字典比较麻烦。为了方便，自己特意写了一个小函数f_selectall，针对SqlServer、Oracle和PostgreSQL数据库分别写了。

核心思想：先查出每张表的列名字段，然后合并列。

一、SqlServer版本：

create function f_selectall
(   
    @ptablename VARCHAR(50),----表名 如SA_WL_LYTZ
    @split VARCHAR(50)  -----别名，如a
)
RETURNS VARCHAR(3000) 
as
BEGIN
    declare @split1 VARCHAR(50);
    declare @split2 VARCHAR(50);
    declare @sreturn VARCHAR(3000);

    if(@split is null)
      set @split1= ''
   ELSE
    set @split1= @split --select ltrim(RTRIM(@split)) 

    if( @split1 <> '')
          set @split2 = @split1+'.';
    ELSE
        set @split2 = @split1 ;

      set @sreturn = (select 'select '+cols+' from '+TABLE_NAME+' '+@split1 from 
                  (SELECT   DISTINCT TABLE_NAME,STUFF((SELECT ','+@split2+ COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS 
                  WHERE TABLE_NAME = A.TABLE_NAME FOR XML PATH('')),1,1,'') AS cols
                  FROM INFORMATION_SCHEMA.COLUMNS  AS A
                  where table_name = UPPER(@ptablename)) t);

    RETURN @sreturn
END　　

   使用的时候只需：select  dbo.f_selectall('TABLE','a') ，即可。

   输出结果为：select a.col1,a.col2,a.col3 from TABLE a ；

   完美代替 select a.* from table a ;

   如果不想用别名a，直接空着即可，即select  dbo.f_selectall('TABLE','')，

   输出结果为：select col1,col2,col3 from TABLE ；

   Sqlserver获取列名语句：

SELECT * FROM INFORMATION_SCHEMA.COLUMNS where table_name = '表名'

二、Oracle版本：

CREATE OR REPLACE FUNCTION F_SELECTALL (v_table IN VARCHAR2, v_prefix IN VARCHAR2)
   RETURN VARCHAR2
IS
   Rtsql   VARCHAR2 (1000);
   prefix VARCHAR2 (20);
   temp VARCHAR2 (20);
BEGIN
   temp:=trim(v_prefix);
     IF temp is null or temp='' THEN
            prefix:='';
     ELSE
            prefix:=v_prefix||'.';
   END IF;
    select 'select '||t.col||' from '||UPPER(v_table)||' '||v_prefix into Rtsql from 
  (select wm_concat(t1.col) as col from 
        (select prefix||column_name as col from user_tab_columns where Table_Name=UPPER(v_table)) t1
    ) t;
        
    Return Rtsql;
    -----使用： select F_SELECTALL('x_code','a') from dual;
END;

使用： select F_SELECTALL('x_code','a') from dual 

 或：select F_SELECTALL('x_code','') from dual 

 Oracle获取列名语句：

select * from user_tab_columns where Table_Name= '表名'

三、PostgreSQL版本：

CREATE OR REPLACE FUNCTION "tzwork"."f_selectall"("@v_table" varchar, "@v_prefix" varchar)
  RETURNS "pg_catalog"."varchar" AS $BODY$
  declare "@result" varchar;
  declare "@prefix" varchar;
  BEGIN
      if(length(trim("@v_prefix"))>0) then
        "@prefix"="@v_prefix"||'.';
      else
        "@prefix"='';
      end if;
        
        "@result" = ( select 'select '||string_agg("@prefix"||attname ,',')||' from  '||relname||' '||"@v_prefix" from 
                      (select t.* from (
                        select c.relname,col_description(a.attrelid,a.attnum)as comment,a.attname ,format_type(a.atttypid,a.atttypmod) as type,attnotnull as notnull 
                        from pg_class c,pg_attribute a 
                        where c.relname="@v_table" and c.oid=a.attrelid and a.attnum>0  
                      ) t where length(type) > 1)test
                      group by relname 
                    ); 
        
  RETURN "@result";
END$BODY$
  LANGUAGE plpgsql VOLATILE
  COST 100　

使用： select F_SELECTALL('x_code','a')

或：select F_SELECTALL('x_code','')

PostgreSQL获取列名语句

select c.relname,col_description(a.attrelid,a.attnum)as comment,a.attname ,format_type(a.atttypid,a.atttypmod) as type,attnotnull as notnull 
from pg_class c,pg_attribute a 
where c.relname='表名' and c.oid=a.attrelid and a.attnum>0  

四、Mysql版本

DROP FUNCTION IF EXISTS f_selectall;

DELIMITER $ 
CREATE FUNCTION f_selectall(ptablename VARCHAR(50),split VARCHAR(50))
RETURNS VARCHAR(300)
BEGIN
    declare split1 VARCHAR(50);
    declare split2 VARCHAR(50);
    declare sreturn VARCHAR(3000);
        
        select if(ISNULL(split),'',LTRIM(RTRIM(split))) into split1;
        select if(split1='',split1,CONCAT(split1,'.')) into split2;
                
        select CONCAT('select ',t.col,CONCAT(' from ',ptablename,' ',split1) ) into sreturn
        from 
    (select GROUP_CONCAT(CONCAT('a.',COLUMN_NAME)) col from information_schema.COLUMNS where table_name = ptablename ) t ;
        
        
        RETURN sreturn;
 END $

DELIMITER ;

使用： select F_SELECTALL('x_code','a')

 或：select F_SELECTALL('x_code','')

 Mysql获取列名语句：

select * from information_schema.COLUMNS where table_name = '表名'

　　

自用小工具，工作中可以提高效率。