如何以更易維護的方式創建帶有前綴的表

Question

我需要維護一個SQL腳本（對於MySQL），它創建了許多具有相同前綴的表，如wp_parent，wp_teacher。我不想寫CREATE TABLE wp_parent。在這種情況下，如果我需要更改前綴，我必須修改很多行。

我試圖使用MySQL user variable，但它沒有奏效。

有什麼辦法讓前綴變成變量然後在其他語句中使用變量？

還有其他方法可以使腳本更易維護嗎？

Answer 1

您可以使用此命令將添加前綴表中的數據庫

SELECT Concat('ALTER TABLE ', TABLE_NAME, ' RENAME TO dr_', TABLE_NAME, ';') 
FROM INFORMATION_SCHEMA.TABLES; 

試試看！

Answer 2

mysql> drop database if exists prefixdb; 
Query OK, 4 rows affected (0.01 sec) 

mysql> create database prefixdb; 
Query OK, 1 row affected (0.00 sec) 

mysql> use prefixdb 
Database changed 
mysql> create table tab1 (num int) ENGINE=MyISAM; 
Query OK, 0 rows affected (0.05 sec) 

mysql> create table tab2 like tab1; 
Query OK, 0 rows affected (0.05 sec) 

mysql> create table tab3 like tab1; 
Query OK, 0 rows affected (0.05 sec) 

mysql> create table tab4 like tab1; 
Query OK, 0 rows affected (0.04 sec) 

mysql> show tables; 
+--------------------+ 
| Tables_in_prefixdb | 
+--------------------+ 
| tab1    | 
| tab2    | 
| tab3    | 
| tab4    | 
+--------------------+ 
4 rows in set (0.00 sec) 
The query to generate it would be 

select 
    concat('alter table ',db,'.',tb,' rename ',db,'.',prfx,tb,';') 
from 
    (select table_schema db,table_name tb 
    from information_schema.tables where 
    table_schema='prefixdb') A, 
    (SELECT 'dr_' prfx) B 
; 
Running it at the command line I get this: 

mysql> select concat('alter table ',db,'.',tb,' rename ',db,'.',prfx,tb,';') from (select table_schema db,table_name tb from information_schema.tables where table_schema='prefixdb') A,(SELECT 'dr_' prfx) B; 
+----------------------------------------------------------------+ 
| concat('alter table ',db,'.',tb,' rename ',db,'.',prfx,tb,';') | 
+----------------------------------------------------------------+ 
| alter table prefixdb.tab1 rename prefixdb.dr_tab1;    | 
| alter table prefixdb.tab2 rename prefixdb.dr_tab2;    | 
| alter table prefixdb.tab3 rename prefixdb.dr_tab3;    | 
| alter table prefixdb.tab4 rename prefixdb.dr_tab4;    | 
+----------------------------------------------------------------+ 
4 rows in set (0.00 sec) 
Pass the result back into mysql like this: 

mysql -hhostip -uuser -pass -AN -e"select concat('alter table ',db,'.',tb,' rename ',db,'.',prfx,tb,';') from (select table_schema db,table_name tb from information_schema.tables where table_schema='prefixdb') A,(SELECT 'dr_' prfx) B" | mysql -hhostip -uuser -ppass -AN 
With regard to your question if you want to rename all tables, do not touch information_schema and mysql databases. Use this query instead: 

select 
    concat('alter table ',db,'.',tb,' rename ',db,'.',prfx,tb,';') 
from 
    (select table_schema db,table_name tb 
    from information_schema.tables where 
    table_schema not in ('information_schema','mysql')) A, 
    (SELECT 'dr_' prfx) B ;