如果存在则更改表或如果不存在则创建

MySQL INFORMATION_SCHEMA database to the rescue:

-- First check if the table exists
IF EXISTS(SELECT table_name 
            FROM INFORMATION_SCHEMA.TABLES
           WHERE table_schema = 'db_name'
             AND table_name LIKE 'wild')

-- If exists, retreive columns information from that table
THEN
   SELECT COLUMN_NAME, DATA_TYPE, IS_NULLABLE, COLUMN_DEFAULT
     FROM INFORMATION_SCHEMA.COLUMNS
    WHERE table_name = 'tbl_name'
      AND table_schema = 'db_name';

   -- do some action, i.e. ALTER TABLE if some columns are missing 
   ALTER TABLE ...

-- Table does not exist, create a new table
ELSE
   CREATE TABLE ....

END IF;

更多信息:

• MySQL 参考手册:第 19 章 INFORMATION_SCHEMA 表
• MySQL 参考手册:INFORMATION_SCHEMA TABLES 表
• MySQL 参考手册:INFORMATION_SCHEMA COLUMNS 表

更新:

另一个可能更简单的选择是删除现有表并使用新模式重新创建它.为此，您需要:

CREATE TABLE old_table_copy LIKE old_table;

INSERT INTO old_table_copy
SELECT * FROM old_table;

DROP TABLE old_table;

CREATE TABLE new_table (...new values...);

INSERT INTO new_table ([... column names from old table ...])
SELECT [...column names from old table ...] 
FROM old_table_copy;

DROP TABLE old_table_copy;