Sql updating a table from itself
Sql updating a table from itself - dating bath spa
to allow inserting and updating exactly the desired data.These features provide a lot of power and flexibility, making My SQL significantly more capable than it otherwise might be.
Remarks The has special behavior for update operations, where it is updated to the current timestamp value when not explicitly updated with a different value.
What I want to do is either insert only the new rows, or insert the new rows and update the changed rows (depending on the scenario). If I want to insert only the rows that will not violate the unique index, I can: Which method to use largely depends on requirements.
If the software must support multiple database backends or versions, perhaps the generic, standard queries are the best bet.
Refer to the discussion of these types in the Data Types topic for more details. This command must be run on the master aggregator or a child aggregator node.
For more information, see Node Requirements for Mem SQL Commands.
Which value will be chosen is implementation-defined and unspecified.
In general, even different executions of the same command with the same data may produce different results when a non-deterministic update is specified. expr An expression that evaluates to a valid column-type value for the specified column.where_condition One or more expressions that evaluate to true for each row to update.If performance is the goal and the queries don’t need to be portable, I see no reason not to use the solution that performs best.If the software must support multiple database backends performance is critical, there’s probably no way to avoid writing different queries for each supported backend.It was non-standard behaviour that was fixed in version 2.5.