Stored Procedures and Functions

Stored Procedures and Functions
Dichiarazione di procedure e funzioni
CREATE
[DEFINER = { user | CURRENT_USER }]
PROCEDURE sp_name ([proc_parameter[,...]])
[characteristic ...] routine_body
CREATE
[DEFINER = { user | CURRENT_USER }]
FUNCTION sp_name ([func_parameter[,...]])
RETURNS type
[characteristic ...] routine_body
Dichiarazione di procedure e funzioni
proc_parameter:
[ IN | OUT | INOUT ] param_name type
func_parameter:
param_name type
type:
Any valid MySQL data type
characteristic:
LANGUAGE SQL
| [NOT] DETERMINISTIC
| { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA }
| SQL SECURITY { DEFINER | INVOKER }
| COMMENT 'string'
routine_body:
Valid SQL procedure statement
Definizione di procedure e funzioni
[begin_label:] BEGIN
[statement_list]
END [end_label]
BEGIN ... END syntax is used for writing compound statements, which can appear within stored programs. A compound statement can contain multiple statements, enclosed by the BEGIN and END keywords. statement_list represents a list of one or more statements, each terminated by a semicolon (;) statement delimiter
Ritorno di una funzione
RETURN expr
The RETURN statement terminates execution of a stored function and returns the value expr to the function caller.
Chiamata di una procedura
CALL sp_name([parameter[,...]])
CALL sp_name[()] The CALL statement invokes a stored procedure that was defined previously with CREATE PROCEDURE. As of MySQL 5.0.30, stored procedures that take no arguments can be invoked without parentheses. That is, CALL p() and CALL p are equivalent. Dichiarazione di variabili locali
DECLARE var_name [, var_name] ... type [DEFAULT value]
This statement is used to declare local variables within stored programs. To provide a default value for the variable, include a DEFAULT clause. The value can be specified as an expression; it need not be a constant. If the DEFAULT clause is missing, the initial value is NULL. Dichiarazione di Conditions
DECLARE condition_name CONDITION FOR condition_value
condition_value:
SQLSTATE [VALUE] sqlstate_value
| mysql_error_code
Dichiarazione di handler
DECLARE handler_type HANDLER
FOR condition_value [, condition_value] ...
statement
handler_type:
CONTINUE
| EXIT
| UNDO
The DECLARE ... HANDLER statement specifies handlers that each may deal with one or more conditions. If one of condition_value:
these conditions occurs, the SQLSTATE [VALUE] sqlstate_value
specified statement is | condition_name
executed. | SQLWARNING
| NOT FOUND
| SQLEXCEPTION
| mysql_error_code
Assegnazione
SET var_name = expr [, var_name = expr] ... The SET statement in stored programs is an extended version of the general SET statement.
Assegnazione
SELECT col_name [, col_name] ...
INTO var_name [, var_name] ...
table_expr
SELECT ... INTO syntax enables selected columns to be stored directly into variables. The query should return a single row. If the query returns no rows, a warning with error code 1329 occurs (No data), and the variable values remain unchanged. If the query returns multiple rows, error 1172 occurs. Use LIMIT 1 to limit the result set to a single row. Cursors
A cursor allows access to the result of a select row by row. Cursors are supported inside stored procedures and functions and triggers. The syntax is as in embedded SQL. Cursors in MySQL have these properties:
•
Asensitive: The server may or may not make a copy of its result table
•
Read only: Not updatable
• Nonscrollable: Can be traversed only in one direction and cannot skip rows
Cursors must be declared before declaring handlers. Variables and conditions must be declared before declaring either cursors or handlers. Utilizzo di cursori
DECLARE cursor_name CURSOR FOR select_statement
OPEN cursor_name This statement opens a previously declared cursor. FETCH cursor_name INTO var_name [, var_name] ... This statement fetches the next row (if a row exists) using the specified open cursor, and advances the cursor pointer. CLOSE cursor_name This statement closes a previously opened cursor. Costrutto IF
IF search_condition THEN statement_list [ELSEIF
search_condition THEN statement_list] ... [ELSE
statement_list] END IF implements a basic conditional construct. If the search_condition evaluates to true, the corresponding SQL statement list is executed. If no search_condition matches, the statement list in the ELSE clause is executed. Each statement_list consists of one or more statements. Costrutto CASE
CASE case_value
WHEN when_value THEN statement_list
[WHEN when_value THEN statement_list] ...
[ELSE statement_list]
END CASE
Or:
CASE
WHEN search_condition THEN statement_list
[WHEN search_condition THEN statement_list] ...
[ELSE statement_list]
END CASE
The CASE statement for stored programs implements a complex conditional construct. If a search_condition evaluates to true, the corresponding SQL statement list is executed. If no search condition matches, the statement list in the ELSE clause is executed.
Ciclo LOOP
[begin_label:] LOOP
statement_list
END LOOP [end_label]
LOOP implements a simple loop construct, enabling repeated execution of the statement list.
Ciclo REPEAT … UNTIL
[begin_label:] REPEAT
statement_list
UNTIL search_condition
END REPEAT [end_label]
The statement list within a REPEAT statement is repeated until the search_condition is true. Thus, a REPEAT always enters the loop at least once.
Ciclo WHILE
[begin_label:] WHILE search_condition DO
statement_list
END WHILE [end_label]
The statement list within a WHILE statement is repeated as long as the search_condition is true.
LEAVE and ITERATE
LEAVE label
This statement is used to exit the flow control construct that has the given label. It can be used within BEGIN ... END or loop constructs (LOOP, REPEAT, WHILE). ITERATE label
ITERATE can appear only within LOOP, REPEAT, and WHILE statements. ITERATE means “do the loop again.”
Trigger
CREATE
[DEFINER = { user | CURRENT_USER }]
TRIGGER trigger_name trigger_time trigger_event
ON tbl_name FOR EACH ROW trigger_stmt
A trigger is a named database object that is associated with a table, and that activates when a particular event occurs for the table. You cannot associate a trigger with a TEMPORARY table or a view.
Trigger
trigger_time is the trigger action time. It can be BEFORE or AFTER to indicate that the trigger activates before or after each row to be modified.
trigger_event indicates the kind of statement that activates the trigger. it can be one of the following:
INSERT: The trigger is activated whenever a new row is inserted into the table; UPDATE: The trigger is activated whenever a row is modified; DELETE: The trigger is activated whenever a row is deleted from the table; Event
CREATE [DEFINER = { user | CURRENT_USER }] EVENT
[IF NOT EXISTS] event_name ON SCHEDULE schedule
[ON COMPLETION [NOT] PRESERVE] [ENABLE | DISABLE | DISABLE ON SLAVE] [COMMENT 'comment'] DO sql_statement; schedule: AT timestamp [+ INTERVAL interval] ... | EVERY interval [STARTS timestamp [+ INTERVAL interval] ...] [ENDS timestamp [+ INTERVAL interval] ...]
interval: quantity {YEAR | QUARTER | MONTH | DAY | HOUR | MINUTE | WEEK | SECOND | YEAR_MONTH | DAY_HOUR | DAY_MINUTE | DAY_SECOND | HOUR_MINUTE | HOUR_SECOND | MINUTE_SECOND}