Difference between revisions of "CREATE TRIGGER"
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==Purpose== | ==Purpose== | ||
Creates a trigger for a table | Creates a trigger for a table | ||
| − | |||
==Syntax== | ==Syntax== | ||
CREATE TRIGGER ON [<database>!]<table> | CREATE TRIGGER ON [<database>!]<table> | ||
| − | FOR | + | FOR DELETE | ONAFTERDELETE | INSERT | ONAFTERINSERT | UPDATE | ONAFTERUPDATE |
AS <expression> | AS <expression> | ||
| − | |||
==See Also== | ==See Also== | ||
| − | [[ADD TABLE]], [[ALTER INDEX]], [[ALTER TABLE]], [[SQL Constraints|CONSTRAINTS]], [[SQL Data Types|DATA TYPES | + | [[ADD TABLE]], [[ALTER INDEX]], [[ALTER TABLE]], [[SQL Constraints|CONSTRAINTS]], [[SQL Data Types|DATA TYPES]], [[DELETE TRIGGER]], [[DROP TABLE]], [[GETENV()]], [[SQL INSERT|INSERT]], [[SQL SELECT|SELECT]], [[SET AUTOCATALOG]], [[SET XMLFORMAT]], |
| − | + | ||
==Description== | ==Description== | ||
The CREATE TRIGGER command is used to create a trigger for the specified table. Triggers cause the logical <expression> to be evaluated when certain operations are attempted. | The CREATE TRIGGER command is used to create a trigger for the specified table. Triggers cause the logical <expression> to be evaluated when certain operations are attempted. | ||
| − | + | {| class="wikitable" width="100%" | |
| − | + | !width="50%"|Trigger||Operation | |
| − | {| class="wikitable" | + | |
| − | !Trigger||Operation | + | |
|- | |- | ||
| − | | | + | |valign="top"|DELETE||Attempt to delete an existing record. Corresponds to onbeforedelete trigger in listings. |
|- | |- | ||
| − | | | + | |valign="top"|ONAFTERDELETE||After deleting an existing record |
|- | |- | ||
| − | | | + | |valign="top"|INSERT||Attempt to add a new record. Corresponds to onbeforeinsert trigger in listings. |
| + | |- | ||
| + | |valign="top"|ONAFTERINSERT||After adding a new record | ||
| + | |- | ||
| + | |valign="top"|UPDATE||Attempt to modify an existing record. Corresponds to onbeforeupdate trigger in listings. | ||
| + | |- | ||
| + | |valign="top"|ONAFTERUPDATE||After modifying an existing record | ||
|- | |- | ||
|} | |} | ||
| − | |||
If the <expression> evaluates to False (.F.) the operation does not complete. If the <expression> evaluates to True (.T.) the operations does complete. | If the <expression> evaluates to False (.F.) the operation does not complete. If the <expression> evaluates to True (.T.) the operations does complete. | ||
| − | + | {| class="wikitable" width="100%" | |
| − | {| class="wikitable" | + | !width="50%"|Keywords||Description |
| − | !Keywords||Description | + | |
|- | |- | ||
| − | |database||The name of the database to which the table belongs | + | |valign="top"|database||The name of the database to which the table belongs. |
|- | |- | ||
|table||The name of the table | |table||The name of the table | ||
|- | |- | ||
| − | |FOR UPDATE | | + | |FOR DELETE | ONAFTERDELETE | INSERT | ONAFTERINSERT | UPDATE | ONAFTERUPDATE||valign="top"|Specifies the type of trigger to be created. |
|- | |- | ||
|expression||A logical expression to be evaluated | |expression||A logical expression to be evaluated | ||
|- | |- | ||
|} | |} | ||
| − | |||
==Example== | ==Example== | ||
<code lang="recital"> | <code lang="recital"> | ||
| − | + | CREATE TRIGGER ON customers FOR UPDATE AS not empty(custid) | |
| − | CREATE TRIGGER ON | + | |
</code> | </code> | ||
| − | + | ||
| − | + | ||
| − | + | ||
| − | + | ||
[[Category:Documentation]] | [[Category:Documentation]] | ||
[[Category:SQL]] | [[Category:SQL]] | ||
[[Category:Commands]] | [[Category:Commands]] | ||
| − | [[Category:Triggers]] | + | [[Category:Databases]] |
| + | [[Category:Lianja VFP Extensions]] | ||
| + | [[Category:VFP Command Extensions]] | ||
| + | [[Category:Database Triggers]] | ||
Latest revision as of 09:36, 22 December 2017
Contents
Purpose
Creates a trigger for a table
Syntax
CREATE TRIGGER ON [<database>!]<table>
FOR DELETE | ONAFTERDELETE | INSERT | ONAFTERINSERT | UPDATE | ONAFTERUPDATE
AS <expression>
See Also
ADD TABLE, ALTER INDEX, ALTER TABLE, CONSTRAINTS, DATA TYPES, DELETE TRIGGER, DROP TABLE, GETENV(), INSERT, SELECT, SET AUTOCATALOG, SET XMLFORMAT,
Description
The CREATE TRIGGER command is used to create a trigger for the specified table. Triggers cause the logical <expression> to be evaluated when certain operations are attempted.
| Trigger | Operation |
|---|---|
| DELETE | Attempt to delete an existing record. Corresponds to onbeforedelete trigger in listings. |
| ONAFTERDELETE | After deleting an existing record |
| INSERT | Attempt to add a new record. Corresponds to onbeforeinsert trigger in listings. |
| ONAFTERINSERT | After adding a new record |
| UPDATE | Attempt to modify an existing record. Corresponds to onbeforeupdate trigger in listings. |
| ONAFTERUPDATE | After modifying an existing record |
If the <expression> evaluates to False (.F.) the operation does not complete. If the <expression> evaluates to True (.T.) the operations does complete.
| Keywords | Description |
|---|---|
| database | The name of the database to which the table belongs. |
| table | The name of the table |
| FOR DELETE | ONAFTERDELETE | INSERT | ONAFTERINSERT | UPDATE | ONAFTERUPDATE | Specifies the type of trigger to be created. |
| expression | A logical expression to be evaluated |
Example
CREATE TRIGGER ON customers FOR UPDATE AS not empty(custid)
