場景2：

根據兩個欄位的值組合情況去自定義第三個欄位

原始表：

目標：根據欄位S_INFO_WINDCODE中的值的SH和SZ，與S_INFO_LISTBOARDNAME中的值組合構成一個第三個欄位MARKET_LISTBOARDNAME，也即如下表

    解決思路：

-- 建立列名MARKET
SET @dbname = DATABASE();
SET @tablename = "asharedescription";
SET @columnname = "MARKET";
SET @preparedStatement = (SELECT IF(
  (
    SELECT COUNT(*) FROM INFORMATION_SCHEMA.COLUMNS
    WHERE
      (table_name = @tablename)
      AND (table_schema = @dbname)
      AND (column_name = @columnname)
  ) > 0,
  "SELECT 1",
  CONCAT("ALTER TABLE ", @tablename, " ADD ", @columnname, " VARCHAR(10) NOT NULL default 'NO';")
));
PREPARE alterIfNotExists FROM @preparedStatement;
EXECUTE alterIfNotExists;
DEALLOCATE PREPARE alterIfNotExists;

-- 建立列名MARKET_LISTBOARDNAME
SET @dbname = DATABASE();
SET @tablename = "asharedescription";
SET @columnname = "MARKET_LISTBOARDNAME";
SET @preparedStatement = (SELECT IF(
  (
    SELECT COUNT(*) FROM INFORMATION_SCHEMA.COLUMNS
    WHERE
      (table_name = @tablename)
      AND (table_schema = @dbname)
      AND (column_name = @columnname)
  ) > 0,
  "SELECT 1",
  CONCAT("ALTER TABLE ", @tablename, " ADD ", @columnname, " VARCHAR(10) NOT NULL default 'NO';")
));
PREPARE alterIfNotExists FROM @preparedStatement;
EXECUTE alterIfNotExists;
DEALLOCATE PREPARE alterIfNotExists;

-- 生成組合的資料
SELECT a.s_info_windcode,
substring_index(a.S_INFO_WINDCODE, '.', -1) MARKET,
a.S_INFO_LISTBOARDNAME,
CASE 
  WHEN substring_index(a.S_INFO_WINDCODE, '.', -1)='SH' AND S_INFO_LISTBOARDNAME='主機板' THEN '滬市A股'
  WHEN substring_index(a.S_INFO_WINDCODE, '.', -1)='SZ' AND S_INFO_LISTBOARDNAME='主機板' THEN '深A主機板'
  WHEN S_INFO_LISTBOARDNAME='中小企業板' THEN '中小板'
  WHEN S_INFO_LISTBOARDNAME='創業板' THEN '創業板'
  ELSE NULL END MARKET_LISTBOARDNAME
FROM asharedescription a;

-- 更新資料
UPDATE asharedescription ad,
(
-- start 生成組合的資料  
SELECT a.s_info_windcode,
substring_index(a.S_INFO_WINDCODE, '.', -1) MARKET,
a.S_INFO_LISTBOARDNAME,
CASE 
  WHEN substring_index(a.S_INFO_WINDCODE, '.', -1)='SH' AND S_INFO_LISTBOARDNAME='主機板' THEN '滬市A股'
  WHEN substring_index(a.S_INFO_WINDCODE, '.', -1)='SZ' AND S_INFO_LISTBOARDNAME='主機板' THEN '深A主機板'
  WHEN S_INFO_LISTBOARDNAME='中小企業板' THEN '中小板'
  WHEN S_INFO_LISTBOARDNAME='創業板' THEN '創業板'
  ELSE NULL END MARKET_LISTBOARDNAME
FROM asharedescription a
-- end 生成組合的資料  
) AS tt
SET ad.MARKET = tt.MARKET,ad.MARKET_LISTBOARDNAME = tt.MARKET_LISTBOARDNAME
WHERE tt.S_INFO_WINDCODE = ad.S_INFO_WINDCODE;