Mysql updating multiple tables
More exotic databases link tables together relationally, so that specific values that might appear in hundreds of tables only need to be defined in one (a topic to be covered later).
I've always thought that direct experience is a good way to inspire confidence in one's abilities, so we'll start out by creating a database and a table at the keyboard, by direct interaction with My SQL.
These articles will familiarize the reader with basic database concepts, move on to My SQL, and show how to create a useful database, step by step.
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Even worse, the CASE method was 41.1x slower than the INSERT method w/ 30,000 records (6.1x slower than TRANSACTION). INSERT and CASE methods broke even at ~1,000 records.
Even at 100 records, the CASE method is BARELY faster.
These options apply to all storage engines unless otherwise indicated.
Options that do not apply to a given storage engine may be accepted and remembered as part of the table definition.
Table options are used to optimize the behavior of the table.
In most cases, you do not have to specify any of them.
UPDATE table SET Col1 = 1 WHERE id = 1; UPDATE table SET Col1 = 2 WHERE id = 2; UPDATE table SET Col2 = 3 WHERE id = 3; UPDATE table SET Col1 = 10 WHERE id = 4; UPDATE table SET Col2 = 12 WHERE id = 4; If there is no duplicates then i dont want that row to be inserted. because i am fetching information from another site which maintains tables with id's. if the site has new records then i will end up inserting only the ids and count except all other information.
if and only if there is an entry for the id then it should update else it should skip. $operation Checked) $command Txt .= " WHEN $operation ID THEN $operation Checked "; $command Txt .= ' ELSE id END WHERE id IN ('.implode(', ', array_keys(block Operation Checked )).');'; variant, a variant with "case / when / then" clause and a naive approach with transaction. The overall conclusion is that the variant with case statement turns out to be twice as fast as two other variants, but it's quite hard to write correct and injection-safe code for it, so I personally stick to the simplest approach: using transactions.
(Because the procedure for installing My SQL is different on each platform, and because the installation process is nearly automatic in modern times, I've decided not to cover installation issues.
At this point I assume the reader has successfully installed My SQL and has logon authority in the system.) Start the My SQL command-line application I'll make this one concession to the differences between platforms: NOTE: There's an alternative to telling My SQL which database to use — one simply prepends the database name to each table reference, like this: "database_name.table_name".
For more information, see Section 188.8.131.52, “CREATE TABLE Statement Retention”.