how to use an IF statement in oracle's INSERT syntax like mssql server?

hi,
I am using mssql with oledb,
I have this sql text like:

;===========================================
IF (select count(*) from table_user where userid=1700))=0
INSERT INTO table_user (userid,username)
VALUES (1700,'azsd')
;===========================================

now our database moved to oracle 9i,
I use the "if" like this,sure its only occur an oledberror,nothing inserted.

;============================================
IF NOT EXISTS(select userid from table_user where userid=1700) THEN
INSERT INTO table_user (userid,username)
VALUES (1700,'azsd')
END IF
;============================================

I have another idea plan to use when state ments to insert the exists user into an other temp table but i think my methods were so ugly.

how can I do an check before insert in one query?

thx.
azsdAsked:
Who is Participating?
 
izblankConnect With a Mentor Commented:
MERGE INTO TABLE_USER T
   USING (SELECT CAST(1700 as NUMBER) userid, CAST('azsd' AS VARCHAR2(200)) username
           FROM dual) S
   ON (T.userid = S.userid)
   WHEN MATCHED THEN UPDATE SET T.username=t.username
   WHEN NOT MATCHED THEN INSERT (T.userid,T.username)
   VALUES (S.userid, S.username);
0
 
RaisinJCommented:
Decalre another variable...

@User_ID    Table_User.UserID%Type;

SELECT NVL(UserID,0)
INTO @User_ID
FROM Table_User
WHERE User_ID = 1700

IF @User_ID = 0
    INSERT INTO Table_User (UserID, UserName)
    VALUES (1700,'@YourUserName');
END IF;
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azsdAuthor Commented:
thx your reply

I only can using query command,store procedure/function not suitable for my programing library....
it seems kololedb don't have that feather....

seems your solution are only suite in procedure,in sql plus it said:

@User_ID    table_user.UserID%Type;
*
Line 1 occured error:
ORA-00900: invalied SQL statements....

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ishandoCommented:
The @ symbols is used in MS SQL Server to identify variables.
In Oracle the @ symbol is used as a short hand for the 'start' command which executes script files.

Try the above solution without the @ symbols.

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RaisinJCommented:
Sorry, in your variable declaration, you cannot use the "@" symbol.  If you did, try doing it without the "@" symbol.
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grim_toasterConnect With a Mentor Commented:
Oracle does not have an insert unless command natively, so you will need to use some form of PL/SQL code to do this.  Going by your comment that you cannot use stored procedures/functions, I would suggest an anonymous PL/SQL block.

The way it would be implemented would be dependent on what would be the normal execution of the code.  If you can put a unique constraint/index on the userid column (going by what you are trying to do I think this should be there anyway), then simply doing the insert and handling a duplicate value on index exception would be simply:

DECLARE
    p_userid   TABLE_USER.userid%TYPE   := 17;
    p_username TABLE_USER.username%TYPE := 'me';
BEGIN
    INSERT INTO TABLE_USER (userid, username)
    VALUES (p_userid, p_username);
EXCEPTION
    WHEN DUP_VAL_ON_INDEX THEN
        -- ignore...
        NULL;
END;

However, the other option would be to do similar to what was provided previously, however, with the syntax correction, and the removal of the NVL (which would cause it to never work):

DECLARE
    p_userid   TABLE_USER.userid%TYPE   := 18;
    p_username TABLE_USER.username%TYPE := 'me';
    l_tmp NUMBER;
BEGIN
    SELECT COUNT(*)
    INTO   l_tmp
    FROM   TABLE_USER
    WHERE  userid = p_userid;

    IF (l_tmp = 0) THEN
        INSERT INTO TABLE_USER (userid,username)
        VALUES (p_userid, p_username);
    END IF;
END;
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azsdAuthor Commented:
yes,by little modify,these two nice script works!
0
 
azsdAuthor Commented:
thx all yours,
I am going to modify my codes now.
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