MySQL insert row on duplicate key update multiple columns

Question

I have a table (name, date, stat1, stat2, stat3), (name, date) is the PK. When I insert rows, there will be duplicate keys, and I need to sum up th

Answer 1

If you specify ON DUPLICATE KEY UPDATE, and a row is inserted that would cause a duplicate value in a UNIQUE index or PRIMARY KEY, MySQL performs an UPDATE of the old row. For example, if column a is declared as UNIQUE and contains the value 1, the following two statements have similar effect:

INSERT INTO table (a,b,c) VALUES (1,2,3) ON DUPLICATE KEY UPDATE c=c+1;

The equivalent update query is as below,

UPDATE table SET c=c+1 WHERE a=1;

If a and b column is unique, equivalent update query would be ,

UPDATE table SET c=c+1 WHERE a=1 OR b=2 LIMIT 1;