hsqldb update on insert

Question

Does anyone know of a solution to make HSQLDB update columns by calling INSERT. I would like my code to be able to insert, and if there's already data, to update that data. I know MySQl, I believe, has 'ON DUPLICATE KEY UPDATE'. I can't seem to find any recent documentation on this.

Answer 1

A good sample is sometimes better the formal documentation on MERGE statement :)

Sample 1

For a table (MY_TABLE) with tho columns (COL_A and COL_B), where the first column is a primary key:

MERGE INTO MY_TABLE AS t USING (VALUES(?,?)) AS vals(a,b) 
        ON t.COL_A=vals.a
    WHEN MATCHED THEN UPDATE SET t.COL_B=vals.b
    WHEN NOT MATCHED THEN INSERT VALUES vals.a, vals.b

Sample 2

Let's add another column (COL_C) to our table:

MERGE INTO MY_TABLE AS t USING (VALUES(?,?,?)) AS vals(a,b,c) 
        ON t.COL_A=vals.a
    WHEN MATCHED THEN UPDATE SET t.COL_B=vals.b, t.COL_C=vals.c
    WHEN NOT MATCHED THEN INSERT VALUES vals.a, vals.b, vals.c

Sample 3

Now let's change the primary key to consist of first two columns (COL_A and COL_B):

MERGE INTO MY_TABLE AS t USING (VALUES(?,?,?)) AS vals(a,b,c) 
        ON t.COL_A=vals.a AND t.COL_B=vals.b
    WHEN MATCHED THEN UPDATE SET t.COL_C=vals.c
    WHEN NOT MATCHED THEN INSERT VALUES vals.a, vals.b, vals.c

Enjoy!