Question

问题

如何更改下面的SQL代码以确保只有在“dbo.tblBootStrapperInstruments”尚不存在时才会插入？

代码

INSERT INTO dbo.tblBootStrapperInstruments (CCY, Instrument, Tenor)
SELECT CCY,Instrument,Gridpoint FROM dbo.Feed_Murex_Intraday_DF mx WHERE NOT EXISTS 
(SELECT * FROM dbo.tblBootStrapperInstruments bs
WHERE bs.CCY = mx.CCY
AND bs.Instrument = mx.Instrument
AND bs.Tenor = mx.Gridpoint)

Answer 1

我是这样做的。

INSERT INTO dbo.tblBootStrapperInstruments (CCY, Instrument, Tenor) 
SELECT mx.CCY,mx.Instrument,mx.Gridpoint FROM dbo.Feed_Murex_Intraday_DF mx
LEFT OUTER JOIN dbo.tblBootStrapperInstruments bs 
ON bs.CCY = mx.CCY 
AND bs.Instrument = mx.Instrument 
AND bs.Tenor = mx.Gridpoint
WHERE bs.CCY IS NULL

Answer 2

您使用的是什么RDBMS？ MySQL的？ MSSQL？ SQLite的？

在MySQL中你有两个选择。您可以在插入值上添加唯一索引，并选择REPLACE statement或使用ON DUPLICATE KEY UPDATE。

Answer 3

如果您的数据库风格和版本支持MERGE，您可以使用它（MERGE已添加到SQL Server 2005）。语法有点笨拙，因为它实际上是通过从另一个表中选择来加载数据。

这个例子使用了Oracle（因为这就是我所拥有的）。

SQL> merge into customer
  2      using ( select 6 as id
  3                     , 'Ella' as forename
  4                     , 'Chip' as surname
  5                     , '1234 Telepath Drive' as address_1
  6                     , 'Milton Lumpky' as address_2
  7                     , 'ML1 4KJ' as postcode
  8                    ,  add_months (sysdate, -235) as date_of_birth
  9               from dual ) t
 10      on (t.id = customer.id )
 11  when not matched then
 12      insert (id, forename, surname, address_1, address_2, postcode, date_of_birth)
 13      values (t.id, t.forename, t.surname, t.address_1, t.address_2, t.postcode, t.date_of_birth)
 14  /

1 row merged.

SQL> commit;

Commit complete.

SQL>

如果我们再次运行相同的查询（ID是主键）它不会失败，它只会合并一行......

SQL> merge into customer
  2      using ( select 6 as id
  3                     , 'Ella' as forename
  4                     , 'Chip' as surname
  5                     , '1234 Telepath Drive' as address_1
  6                     , 'Milton Lumpky' as address_2
  7                     , 'ML1 4KJ' as postcode
  8                    ,  add_months (sysdate, -235) as date_of_birth
  9               from dual ) t
 10      on (t.id = customer.id )
 11  when not matched then
 12      insert (id, forename, surname, address_1, address_2, postcode, date_of_birth)
 13      values (t.id, t.forename, t.surname, t.address_1, t.address_2, t.postcode, t.date_of_birth)
 14  /

0 rows merged.

SQL>

与光头INSERT进行比较和对比......

SQL>   insert into customer (id, forename, surname, address_1, address_2, postcode, date_of_birth)
  2  values ( 6, 'Ella', 'Chip', '1234 Telepath Drive', 'Milton Lumpky', 'ML1 4KJ',add_months (sysdate, -235) )
  3  /
    insert into customer (id, forename, surname, address_1, address_2, postcode, date_of_birth)
*
ERROR at line 1:
ORA-00001: unique constraint (APC.CUS_PK) violated


SQL>

SQL Server（T-SQL）如果不存在则插入

问题

代码

3 个答案: