Mysql updating multiple tables Free live sex without a camera and no sign up with money
Any data that violates any unique index will cause the same problem. For example, I might export some data to a spreadsheet, send it to a client, and the client might update or add some data and return the spreadsheet to me.
That’s a terrible way to update data, but for various reasons, I’m sure many readers have found themselves in a similar situation.
In this article I have discussed several ways to use such non-standard extensions in My SQL for performance and convenience. Not only does it potentially make code non-portable, it can encourage mediocrity by teaching bad habits instead of teaching people the “right” way to do things.
For example, updating multiple tables in a single statement, or inserting and updating at the same time, are definitely strange and ugly things to do.
I belive fully portable or “platform-independent” SQL is mostly a myth.
Writing generic “standard” SQL to the lowest common denominator almost certainly results in under-utilizing the RDBMS’s abilities.
This idea doesn't look possible without using IF EXISTS and sub queries checking for the ID in each table. Then construct an UPDATE query live time as a php string using only the tables where the id was found. re: UPDATE multiple tables I've decided to use four.
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.
To remedy that, we could throw in a where clause to the update statement, as below: -- Better example, but still inefficient update master_table m set m.invoice_amount=( select a.updated_invoice_amount from data_from_accounting a where m.job_number=a.job_number ) where m.job_number in( select a2.job_number from data_from_accounting a2 where m.job_number=a2.job_number ); This would correctly update the records I wanted to update while leaving the others alone, but this query is a little inefficient as it needs to go through the data from accounting twice.
Finally, I came up with a solution that works very efficiently, even with my large 1,000,000-record table.
In this article I’ll give an overview of each feature, help you understand how to choose among them, and point out some things to watch out for. I assume My ISAM tables without support for transactions, with the following sample data: create table t1 ( a int not null primary key, b int not null, c int not null ) type=My ISAM; create table t2 ( d int not null primary key, e int not null, f int not null ) type=My ISAM; insert into t1 (a, b, c) values (1, 2, 3), (2, 4, 6), (3, 6, 9); insert into t2 (d, e, f) values (1, 1, 1), (4, 4, 4), (5, 5, 5); .