Oracle数据库表结构转MySQL表结构

此函数来自部门大佬杰，使用如下
需要将Oracle数据库中的表迁移到MySQL时，需要整理MySQL建表语句，手动整理比较麻烦，尤其是整理列备注语句。此时可以使用下面的函数自动生成MySQL版本语句。

参数：

1、需要转换的表名；
2、是否包含“已存在则删除语句”（DROP TABLE IF EXISTS），默认包含

使用方法：

`SELECT F_LIMS_GET_SQL_FOR_MYSQL('T_LIMS_EQUIPMENT') FROM DUAL;

或

SELECT F_LIMS_GET_SQL_FOR_MYSQL('T_LIMS_EQUIPMENT',0) FROM DUAL;`

将查询结果拷贝出，在MySQL库里执行即可。

函数如下：

```sql
CREATE OR REPLACE FUNCTION F_LIMS_GET_SQL_FOR_MYSQL(PI_TABLENAME IN VARCHAR2,
                                                    PI_ISDROP    IN INTEGER := 1)
  RETURN CLOB IS
  V_TABLENAME         VARCHAR(100);
  V_RET_SQL           VARCHAR2(4000);
  V_SQL_HEADER        VARCHAR2(1000);
  V_SQL_BODY          CLOB;
  V_SQL_INDEX         VARCHAR2(4000);
  V_SQL_TABLE_COMMENT VARCHAR(400);
  V_SQL_PK_COL_LIST   VARCHAR(1000);
  -- 根据当前数据库和表名，生成mysql建表语句
BEGIN
  -- 表名统一为大写
  SELECT UPPER(PI_TABLENAME) INTO V_TABLENAME FROM DUAL;

  SELECT MAX(T.COMMENTS)
    INTO V_SQL_TABLE_COMMENT
    FROM USER_TAB_COMMENTS T
   WHERE T.TABLE_NAME = V_TABLENAME;

  SELECT MAX(WM_CONCAT('`' || A.COLUMN_NAME || '` '))
    INTO V_SQL_PK_COL_LIST
    FROM USER_CONS_COLUMNS A, USER_CONSTRAINTS B
   WHERE A.CONSTRAINT_NAME = B.CONSTRAINT_NAME
     AND B.CONSTRAINT_TYPE = 'P'
     AND A.TABLE_NAME = V_TABLENAME
   GROUP BY A.TABLE_NAME;

  V_SQL_HEADER := '-- ' || V_SQL_TABLE_COMMENT || ' 建表语句' || CHR(13);

  IF PI_ISDROP = 1 THEN
    V_SQL_HEADER := V_SQL_HEADER || 'DROP TABLE IF EXISTS `' || V_TABLENAME || '`;' ||
                    CHR(13);
  END IF;
  V_SQL_HEADER := V_SQL_HEADER || 'CREATE TABLE `' || V_TABLENAME || '`  (';

  -- 表列信息
  SELECT WM_CONCAT(CHR(13) || '`' || T.COLUMN_NAME || '` ' ||
                   (CASE
                      WHEN T.DATA_TYPE = 'VARCHAR2' OR T.DATA_TYPE = 'NVARCHAR2' THEN
                       'VARCHAR(' || T.DATA_LENGTH || ')'
                      WHEN T.DATA_TYPE = 'DATE' THEN
                       'DATETIME'
                      WHEN T.DATA_TYPE = 'CLOB' THEN
                       'MEDIUMTEXT'
                      WHEN T.DATA_TYPE = 'NUMBER' THEN
                       'DECIMAL'
                      WHEN T.COLUMN_NAME = 'ID' THEN
                       'VARCHAR(32)'
                      ELSE
                       T.DATA_TYPE
                    END) || DECODE(T.NULLABLE, 'N', ' NOT NULL ', '') ||
                   ' COMMENT ''' || TC.COMMENTS || '''')
    INTO V_SQL_BODY
    FROM USER_TAB_COLUMNS T
    LEFT JOIN USER_COL_COMMENTS TC
      ON T.TABLE_NAME = TC.TABLE_NAME
     AND T.COLUMN_NAME = TC.COLUMN_NAME
   WHERE T.TABLE_NAME = V_TABLENAME
   ORDER BY T.COLUMN_ID;

  IF V_SQL_PK_COL_LIST IS NOT NULL THEN
    V_SQL_BODY := V_SQL_BODY || ' ,' || CHR(13) || ' PRIMARY KEY (' ||
                  V_SQL_PK_COL_LIST || ')  ';
  END IF;

  -- 表备注
  V_SQL_BODY := V_SQL_BODY || CHR(13) || ') COMMENT = ''' ||
                V_SQL_TABLE_COMMENT || ''';' || CHR(13);

  -- 唯一索引 
  SELECT (WM_CONCAT('@ALTER TABLE `' || A.TABLE_NAME ||
                    '` ADD UNIQUE INDEX (' ||
                    WM_CONCAT('`' || A.COLUMN_NAME || '`') || ');@'))
    INTO V_SQL_INDEX
    FROM USER_CONS_COLUMNS A, USER_CONSTRAINTS B
   WHERE A.CONSTRAINT_NAME = B.CONSTRAINT_NAME
     AND B.CONSTRAINT_TYPE = 'U'
     AND A.TABLE_NAME = V_TABLENAME
   GROUP BY A.TABLE_NAME, A.CONSTRAINT_NAME;

  IF V_SQL_INDEX IS NOT NULL THEN
    V_SQL_INDEX := REPLACE(REPLACE(V_SQL_INDEX, '@,@', CHR(13)), '@', '');
    V_SQL_INDEX := '-- 创建索引' || CHR(13) || V_SQL_INDEX;
  END IF;

  RETURN V_SQL_HEADER || V_SQL_BODY || V_SQL_INDEX;
END;
/