Thus, inspecting columns computed by triggers is another common use-case for RETURNING. If there are triggers ( Chapter 39) on the target table, the data available to RETURNING is the row as modified by the triggers. In a DELETE, the data available to RETURNING is the content of the deleted row. The current time and user name are stamped into the row, together with the type of operation performed on it. This example trigger ensures that any insert, update or delete of a row in the emp table is recorded (i.e., audited) in the empaudit table. In an UPDATE, the data available to RETURNING is the new content of the modified row. A PL/pgSQL Trigger Function for Auditing. Even if you know only some column values, a complete. Of course you can also insert more than one row, but there is no way to insert less than one row. Data is conceptually inserted one row at a time. The first thing to do before a database can be of much use is to insert data. The RETURNING clause is also very useful with INSERT. When a table is created, it contains no data. INSERT INTO users (firstname, lastname) VALUES ('Joe', 'Cool') RETURNING id INSERT INTO table1 ( column1, column2, someInt, someVarChar ) SELECT lumn1, lumn2, 8, 'some string etc.' FROM table2 WHERE table2.ID 7 I've only used this syntax with Access, SQL 2000/2005/Express, MySQL, and PostgreSQL, so those should be covered. For example, when using a serial column to provide unique identifiers, RETURNING can return the ID assigned to a new row:ĬREATE TABLE users (firstname text, lastname text, id serial primary key) The updated column is boolean so you should output TRUE or FALSE (it will work with 1s and 0s but there is no better than your code being clear). However, in the absence of a collation change, a column can be changed from. The correct syntax is: UPDATE SET Other minor improvements: The case expression also needs CASE WHEN .But it can be very handy when relying on computed default values. This configuration is ignored for ON SELECT rules, which are always applied in. This is not so useful in trivial inserts, since it would just repeat the data provided by the client. In an INSERT, the data available to RETURNING is the row as it was inserted. A common shorthand is RETURNING *, which selects all columns of the target table in order. Otherwise, if the list of columns is not specified, the columns. It can contain column names of the command's target table, or value expressions using those columns. Each column in the table not present in the column list will be filled with a null value. The allowed contents of a RETURNING clause are the same as a SELECT command's output list (see Section 7.3). Use of RETURNING avoids performing an extra database query to collect the data, and is especially valuable when it would otherwise be difficult to identify the modified rows reliably. The INSERT, UPDATE, and DELETE commands all have an optional RETURNING clause that supports this. Sometimes it is useful to obtain data from modified rows while they are being manipulated.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |