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What is select for UPDATE?

Contents
  1. What is SELECT for UPDATE in mysql?
  2. What is the use of SELECT for UPDATE in Oracle?
  3. What is SELECT for UPDATE Postgres?
  4. What is SELECT do?
The SELECT FOR UPDATE statement is used to order transactions by controlling concurrent access to one or more rows of a table. It works by locking the rows returned by a selection query, such that other transactions trying to access those rows are forced to wait for the transaction that locked the rows to finish.


What is SELECT for UPDATE in mysql?

A SELECT ... FOR UPDATE reads the latest available data, setting exclusive locks on each row it reads. Thus, it sets the same locks a searched SQL UPDATE would set on the rows.

What is the use of SELECT for UPDATE in Oracle?

The SELECT FOR UPDATE statement allows you to lock the records in the cursor result set. You are not required to make changes to the records in order to use this statement. The record locks are released when the next commit or rollback statement is issued.

What is SELECT for UPDATE Postgres?

The select ... for update acquires a ROW SHARE LOCK on a table. This lock conflicts with the EXCLUSIVE lock needed for an update statement, and prevents any changes that could happen concurrently. All the locks will be released when the transaction ends.

What is SELECT do?

In most applications, SELECT is the most commonly used data manipulation language (DML) command. As SQL is a declarative programming language, SELECT queries specify a result set, but do not specify how to calculate it. ... Examples.Table "T"QueryResultdoes not existSELECT 1+1, 3*2;`1+1` `3*2` 2 6

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