Merge語(yǔ)句可以用來(lái)插入或更新數(shù)據(jù)，取決于數(shù)據(jù)是否已經(jīng)存在。

語(yǔ)法結(jié)構(gòu)：

MERGE INTO table_name --目標(biāo)表，待更新
USING table_name --源表/視圖
ON (condition) --條件語(yǔ)句，若為真，則記錄更新；若為假，則記錄插入
WHEN MATCHED THEN update_clause --條件為真時(shí)，執(zhí)行語(yǔ)句
DELETE where_clause
WHEN NOT MATCHED THEN insert_clause
[LOG ERRORS log_errors_clause reject_limit <integer | unlimited> ]

例子：
新建兩個(gè)表：customer，customer_import

圖片.png

執(zhí)行語(yǔ)句：

MERGE INTO customer c
USING customer_import i
ON (c.customer_id = i.customer_id)
WHEN MATCHED THEN
UPDATE SET
c.first_name = i.first_name,
c.last_name = i.last_name,
c.address_state = i.address_state,
c.email_address = i.email_address
WHEN NOT MATCHED THEN
INSERT (c.customer_id, c.first_name, c.last_name, c.address_state, c.email_address)
VALUES (c.customer_id, c.first_name, c.last_name, c.address_state, c.email_address);

執(zhí)行后的customer表：

圖片.png