Maybe I am missing something, but why not:
UPDATE T SET T.Data = 1 WHERE . . .
With only 2 fields, what could be in your WHERE clause?
Hu Qinan wrote:
A table T contains two fields: T.ID, T.Data.
I want to set its T.Data to one of three values: NULL, 0, 1 according to its T.ID.
This is what I have done:
1. Set all Data to be NULL:
UPDATE T SET Data = NULL;
2. Create a temporary table Temp to store some selected T.ID. Then update the Data of
these records to 1.
SELECT ID FROM T WHERE ...;
UPDATE T INNER JOIN Temp1 ON T.ID = Temp1.ID SET T.Data = 1;
3. Create another tempory table Temp2 to store selected T.ID. Then update these Data
to be 0.
SELECT ID FROM Temp1 WHERE...
UPDATE T INNER JOIN Temp2 ON T.ID = Temp2.ID SET T.Data = 0;
The above sqls are quite efficient, becasue some values are updated three times. Any
suggestions for me to simply the above operations? Thanks a lot.
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