From the manual:
11.2.6. REPLACE Syntax
REPLACE [LOW_PRIORITY | DELAYED]
[INTO] tbl_name [(col_name,...)]
VALUES ({expr | DEFAULT},...),(...),...
Or:
REPLACE [LOW_PRIORITY | DELAYED]
[INTO] tbl_name
SET col_name={expr | DEFAULT}, ...
Or:
REPLACE [LOW_PRIORITY | DELAYED]
[INTO] tbl_name [(col_name,...)]
SELECT ...
REPLACE works exactly like INSERT, except that if an old row in the
table has the same value as a new row for a PRIMARY KEY or a UNIQUE
index, the old row is deleted before the new row is inserted. See
Section 11.2.4, “INSERT Syntax”.
REPLACE is a MySQL extension to the SQL standard. It either inserts, or
deletes and inserts. For another MySQL extension to standard SQL — that
either inserts or updates — see Section 11.2.4.3, “INSERT ... ON
DUPLICATE KEY UPDATE Syntax”.
Note that unless the table has a PRIMARY KEY or UNIQUE index, using a
REPLACE statement makes no sense. It becomes equivalent to INSERT,
because there is no index to be used to determine whether a new row
duplicates another.
On 2015-10-09 03:45, Ashley Sheridan wrote:
Hi All,
This is a bit of an odd one, and while it's largely an SQL problem, it
will have PHP logic because SQL just doesn't have quite the syntax.
I'm sure this is a standard problem that has a standard solution, but
as
of yet, I've not come across said solution.
I need to update a series of data in a DB. Some of it may exist
already,
and some may need to be removed.
Now the typical for updating (but not removing) data and adding new is
the familiar:
INSERT ... ON DUPLICATE KEY UPDATE ...
syntax, but what about those bits which might need removing?
What's the typical solution that any of you use? I normally just empty
all rows of data sharing the common id for the set of data and then
insert new rows, but that seems wasteful to me, and less clean than it
ought to be.
Thanks,
Ash
http://www.ashleysheridan.co.uk
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