Hello, Let me immediately state that I am aware that many people have requested/suggested to have the merge (Oracle) or upsert implemented and that there is a an issue created in Jira.
My question, although related, is a bit different.
In short, in my Java program I need to be able to:
- support INSERT, UPDATE, DELETE and MERGE/UPSERT on a variety of
databases (thus the solution must be standard) - Derby, Oracle, Sybase, MS
SQL
- avoid stored procedures
- be able to addBatch() all those JDBC PreparedStatements and invoke
executeBatch() to efficiently process them
Currently, MERGE/UPSERT has been implemented by executing two statements -
first a JDBC PreparedStatement UPDATE would be executed, and if it returns
0 count, then the INSERT PreparedStatement. This is very inefficient and
cannot be easily refactored to run as a batch. To batch it now I would
have to implement a two-stage approach: to batch first all UPDATE
statements with addBatch(), then invoke executeBatch(), analyze int[] that
it returns and repeat those actions for the batch of the UPDATE
statements. This is complicated, convoluted, difficult to support and
implement.
I tried to create a Prepared Statement for something like this:
IF (EXISTS
(SELECT 1 FROM test_table WHERE PK_INTEGER_BS519=?)
) BEGIN
UPDATE test_table SET
PK_INTEGER_BS519=?,TIME_850T2=?,BIGINT_63J3P=?,REAL_ZAF15=?,SMALLINT_731O9=?,BIT_4027E=?,INTEGER_95FDU=?,BIGINT_K1YYZ=?,DOUBLE_SRS0O=?,VARCHAR_L2NE2=?,VARCHAR_Z0U7L=?,BIT_32CP2=?,VARCHAR_3UD3C=?,BIGINT_1K7S0=?,DOUBLE_7NGCA=?,INTEGER_HMT78=?,DOUBLE_75L55=?,SMALLINT_MP89H=?,REAL_YOVS7=?,INTEGER_371TT=?
WHERE PK_INTEGER_BS519=?
END
ELSE
BEGIN INSERT INTO
test_table(PK_INTEGER_BS519,TIME_850T2,BIGINT_63J3P,REAL_ZAF15,SMALLINT_731O9,BIT_4027E,INTEGER_95FDU,BIGINT_K1YYZ,DOUBLE_SRS0O,VARCHAR_L2NE2,VARCHAR_Z0U7L,BIT_32CP2,VARCHAR_3UD3C,BIGINT_1K7S0,DOUBLE_7NGCA,INTEGER_HMT78,DOUBLE_75L55,SMALLINT_MP89H,REAL_YOVS7,INTEGER_371TT)
VALUES(?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?)
END
Just to find out that Derby doesn't support IF:
So, is there a better and more efficient way to do so in one SQL statement
which can also be (1) batched and (2) standard (so to be supported by
other databases, such as Sybase, Oracle, MS SQL, so that the same code can
be used with all of them)?
Any other suggestions or thoughts would be greatly appreciated.
Pavel.
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