insert if not exists oracle

问题:

I need to be able to run an Oracle query which goes to insert a number of rows, but it also checks to see if a primary key exists and if it does, then it skips that insert. Something like:

INSERT ALL     IF NOT EXISTS( SELECT 1 WHERE fo.primary_key='bar' )     (         INSERT INTO              schema.myFoo fo ( primary_key, value1, value2 )         VALUES             ('bar','baz','bat')     ),      IF NOT EXISTS( SELECT 1 WHERE fo.primary_key='bar1' )     (         INSERT INTO              schema.myFoo fo ( primary_key, value1, value2 )         VALUES             ('bar1','baz1','bat1')     ) SELECT * FROM schema.myFoo; 

Is this at all possible with Oracle?

_{Bonus points if you can tell me how to do this in PostgreSQL or MySQL.}

回答1:

The statement is called MERGE. Look it up, I'm too lazy.

Beware, though, that MERGE is not atomic, which could cause the following effect (thanks, Marius):

SESS1:

create table t1 (pk int primary key, i int); create table t11 (pk int primary key, i int); insert into t1 values(1, 1); insert into t11 values(2, 21); insert into t11 values(3, 31); commit; 

SESS2: insert into t1 values(2, 2);

SESS1:

MERGE INTO t1 d USING t11 s ON (d.pk = s.pk) WHEN NOT MATCHED THEN INSERT (d.pk, d.i) VALUES (s.pk, s.i); 

SESS2: commit;

SESS1: ORA-00001

回答2:

Coming late to the party, but...

With oracle 11.2.0.1 there is a semantic hint that can do this: IGNORE_ROW_ON_DUPKEY_INDEX

Example:

insert /*+ IGNORE_ROW_ON_DUPKEY_INDEX(customer_orders,pk_customer_orders) */   into customer_orders        (order_id, customer, product) values (    1234,     9876,  'K598')      ; 

---

UPDATE: Although this hint works (if you spell it correctly), there are better approaches which don't require Oracle 11R2:

First approach―direct translation of above semantic hint:

begin   insert into customer_orders          (order_id, customer, product)   values (    1234,     9876,  'K698')   ;   commit; exception   when DUP_VAL_ON_INDEX   then ROLLBACK; end; 

Second aproach―a lot faster than both above hints when there's a lot of contention:

begin     select count (*)     into   l_is_matching_row     from   customer_orders     where  order_id = 1234     ;      if (l_is_matching_row = 0)     then       insert into customer_orders              (order_id, customer, product)       values (    1234,     9876,  'K698')       ;       commit;     end if; exception   when DUP_VAL_ON_INDEX   then ROLLBACK; end; 

回答3:

This only inserts if the item to be inserted is not already present.

Works the same as:

if not exists (...) insert ...  

in T-SQL

insert into destination (DESTINATIONABBREV)    select 'xyz' from dual    left outer join destination d on d.destinationabbrev = 'xyz'    where d.destinationid is null; 

may not be pretty, but it's handy :)

回答4:

We can combine the DUAL and NOT EXISTS to archive your requirement:

INSERT INTO schema.myFoo (      primary_key, value1, value2 )  SELECT     'bar', 'baz', 'bat'  FROM DUAL WHERE NOT EXISTS (     SELECT 1      FROM schema.myFoo     WHERE primary_key = 'bar' ); 

回答5:

If you do NOT want to merge in from an other table, but rather insert new data... I came up with this. Is there perhaps a better way to do this?

MERGE INTO TABLE1 a     USING DUAL     ON (a.C1_pk= 6) WHEN NOT MATCHED THEN     INSERT(C1_pk, C2,C3,C4)     VALUES (6, 1,0,1); 

回答6:

It that code is on the client then you have many trips to the server so to eliminate that.

Insert all the data into a temportary table say T with the same structure as myFoo

Then

insert myFoo   select *      from t        where t.primary_key not in ( select primary_key from myFoo)  

This should work on other databases as well - I have done this on Sybase

It is not the best if very few of the new data is to be inserted as you have copied all the data over the wire.

回答7:

DECLARE    tmp NUMBER(3,1); BEGIN   SELECT COUNT(content_id) INTO tmp FROM contents WHERE (condition);   if tmp != 0 then     INSERT INTO contents VALUES (...);   else     INSERT INTO contents VALUES (...);   end if; END; 

I used the code above. It is long, but, simple and worked for me. Similar, to Micheal's code.

回答8:

This is an answer to the comment posted by erikkallen:

Well, try it yourself and tell me whether you get the same error or not:

SESS1:

create table t1 (pk int primary key, i int); create table t11 (pk int primary key, i int); insert into t1 values(1, 1); insert into t11 values(2, 21); insert into t11 values(3, 31); commit; 

SESS2: insert into t1 values(2, 2);

SESS1:

MERGE INTO t1 d USING t11 s ON (d.pk = s.pk) WHEN NOT MATCHED THEN INSERT (d.pk, d.i) VALUES (s.pk, s.i); 

SESS2: commit;

SESS1: ORA-00001

回答9:

If your table is "independent" from others (I mean, it will not trigger a cascade delete or will not set any foreign keys relations to null), a nice trick could be to first DELETE the row and then INSERT it again. It could go like this:

DELETE FROM MyTable WHERE prop1 = 'aaa'; //assuming it will select at most one row!

INSERT INTO MyTable (prop1, ...) VALUES ('aaa', ...);

If your are deleting something which does not exist, nothing will happen.

回答10:

 INSERT INTO schema.myFoo ( primary_key        , value1          , value2         )                          SELECT 'bar1' AS primary_key ,'baz1' AS value1 ,'bat1' AS value2 FROM DUAL WHERE (SELECT 1 AS value FROM schema.myFoo WHERE LOWER(primary_key) ='bar1' AND ROWNUM=1) is null; 

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