Data Base Management System LAB LECTURES

Transcription

1 Data Base Management System LAB LECTURES Taif University faculty of Computers and Information Technology First Semester H A. Arwa Bokhari & A. Khlood Alharthi & A. Aamal Alghamdi

2 OBJECTIVE u Stored Procedure u User Defined Func9ons

3 Procedure Defini9on of stored procedures A stored procedure is a segment of declara3ve SQL statements stored inside the database catalog. A stored procedure can be invoked by triggers, other stored procedures or applica3ons such as Java, C#, PHP, etc.!

4 Procedure Example The GetAllEmployee() stored procedure selects all employees from the employee table.

5 Procedure Example q The first command is DELIMITER //, which is not related to the stored procedure syntax. The DELIMITER statement changes the standard delimiter which is semicolon ( ;) to another. In this case, the delimiter is changed from the semicolon( ;) to double- slashes //. Why do we have to change the delimiter? Because we want to pass the stored procedure to the server as a whole rather than leung mysql tool to interpret each statement at a 3me. Following the END keyword, we use the delimiter // to indicate the end of the stored procedure. The last command ( DELIMITER;) changes the delimiter back to the standard one. q We use the CREATE PROCEDURE statement to create a new stored procedure. We specify the name of stored procedure a[er the CREATE PROCEDURE statement. q The sec3on between BEGIN and END is called the body of the stored procedure. You put the declara3ve SQL statements in the body to handle business logic. In this stored procedure, we use a simple SELECT statement to query data from the products table.

6 Procedure Example In order to execute a procedure use the following syntax:! CALL STORED_PROCEDURE_NAME()

7 PARAMETERS q IN is the default mode. When you define an IN parameter in a stored procedure, the calling program has to pass an argument to the stored procedure. In addi3on, the value of an IN parameter is protected. It means that even the value of the IN parameter is changed inside the stored procedure, its original value is retained a[er the stored procedure ends. In other words, the stored procedure only works on the copy of the IN parameter. q OUT the value of an OUT parameter can be changed inside the stored procedure and its new value is passed back to the calling program. No3ce that the stored procedure cannot access the ini3al value of the OUT parameter when it starts. q INOUT an INOUT parameter is the combina3on of IN parameter and OUT parameter. It means that the calling program may pass the argument, and the stored procedure can modify the INOUT parameter and pass the new value back to the calling program.!

8 Types of Parameters

9 IN - PARAMETERS

10 OUT- PARAMETERS

11 Loop in Stored Procedures

12 User Defined Func9ons Func3ons are a type of stored code and are very similar to procedures. The significant difference is that a func3on is a PL/SQL block that returns a single value. Func3ons can accept one, many, or no parameters, but a func3on must have a return clause in the executable sec3on of the func3on. The datatype of the return value must be declared in the header of the func3on. A func3on is not a stand- alone executable in the way that a procedure is: It must be used in some context. You can think of it as a sentence fragment. A func3on has output that needs to be assigned to a variable, or it can be used in a SELECT statement.!

13 User Defined Func9ons The syntax for crea3ng a func3on is as follows: CREATE FUNCTION sp_name ([func_parameter[,...]]) RETURNS type [characteris2c...] rou2ne_body!

14 User Defined Func9ons The func3on does not necessarily have to have any parameters, but it must have a RETURN value declared in the header, and it must return values for all the varying possible execu3on streams. The RETURN statement does not have to appear as the last line of the main execu3on sec3on, and there may be more than one RETURN statement (there should be a RETURN statement for each excep3on). A func3on may have IN, OUT, or IN OUT parameters. but you rarely see anything except IN parameters.!

15 UDF- Example Func3on Calling Result

16 UDF- Example

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