Updating strings into access database
(It will use placeholders and parameter binding if it thinks it’s appropriate.) If given our second example with two distinct values, will spot that there are two distinct values, 12, and will effect this with two UPDATE statements as described above.Optimising the number of UPDATEs by grouping the distinct SET values can be done in a way which is compatible with most common SQL databases. FROM approach requires knowledge of the specific SQL database being used.So if the caller has a Postgre SQL database, and calls with data to represent our third example (where the target values are all unique), then the Postgre SQL-specific subclass will effect the updates using the table / UPDATE … To match on names we now need to match on two columns.
At the time of writing, the only database-specific subclass is for Postgre SQL. Let’s expand the original table a bit: “name” has now been split into “first_name” and “last_name”.We can easily contrive for an “updates” table to exist by creating a temporary table and populating it.It is relatively straightforward to populate a table with multiple rows with just one query (or at least, far fewer queries than the number of rows desired).But in many cases this only provides a modest improvement as each UPDATE operation still requires a round-trip communication with the database server.In the case where the application server and database server are on different hosts, the round-trip will involve network latency as well.