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Essential SQL Techniques: Variables, Delimiters, and Procedure Creation
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- 2. SUMMARY FROM PREVIOUS LABWORKS. • You can be able to do… • Making Queries. • To create data base, tables. • Generally add values to the table. • How to create different kind of users. • Basic knowledge on constraints. • Grant privileges.
- 3. STORED PROCEDURE. • Letssee how to 1. Creating variable is a simple method as usual. Syntax: DECLARE variable_Name Variable_type; • It’s the basic way to create. • According to your need/design you can make alteration on it. • Below methods are they… To get Default value To get limited count of characters
- 4. 2. Assign valueto the variable. Syntax: SET variable_name = value; • It’s the basic way to create. SET i=59; SET name= “Mercy”;
- 5. • By default,all MySQL clients use a semicolon (;) as a statement delimiter. • A problem arises when creating functions or procedures because they use semicolons as statement delimiters within the function body. • The field delimiter is the character which splits data or text into separate fields and a field is a column within the database. • Delimiters are necessary when creating stored procedures or triggers. Using a custom delimiter can simplify the creation of compound statements. • Let’s see how to create delimiter. Delimiter
- 6. • Easily getinto the point by the example below: • When you consider the table Account on database Salary, Delimiter… As usual you can create Step1:
- 7. Step2: Consider the semicolonin the end of the query. • Just I’m going to replace by the symbol (##). • You can change with any symbols in any count. • Example: • $$ • $$$ • #$ Etc… Syntax: DELIMITER symbol Eg: DELIMITER ## This is the way to create delimiter replace by the symbol (##).
- 8. Step3: • Style ofthe delimiter is applied. • After that if you write the query in usual method, then it will not give the output and it will ask termination from us. • From the figure below you can get it. Input the query in usual method using semicolon Delimiter replaced by the symbol (##). It is expecting something from us/ waiting for the termination/command. Note: As usual according to the query above, it will give the all elements from the table account.
- 9. Step4: Delimiter changed Finish thecommand with new delimiter • Finish the command with appropriate delimiter. • It will give the output according to the command;
- 10. • It willgive the output according to the command with correct delimiter otherwise it won’t give the output; This is the perfect way to write query.
- 11. CREATING PROCEDURE • Syntax: •DELIMITER symbol • CREATE PROCEDURE procedure_name () • BEGIN • …. QUERY… • END delimiter Symbol If you want to change delimiter symbol then you can replace it
- 12. CALLING PROCEDURE If youwant to change delimiter symbol then you can replace it , and you want to call the query with the particular delimiter symbol.. Delimiter is Changed Query is called with new delimiter
- 13. APPLICATION OF PROCEDURE,DELIMITER Changed the delimiter icon with $$ Declare variable Get the output by select Set value Query is called with new delimiter output
- 14. Find out thedifference from previous example …
- 15. • What isthe usage of “drop” .. • What is the difficulty you may face, when you call the existing procedure (with same name) again… • To overcome this problem you can use drop query as usual. • You can drop and call it again
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- 18. On-Site Exercise: 1. Writethe procedure to get grading system on ADBMS Assessment for 3rd year 2nd semester students. (Just for sample…) Consider the key points below: A+ - Marks >85 A - Marks >75 A- - Marks > 70 B+ - Marks >65 B - Marks >60 B- - Marks > 55 C+ - Marks >50 C - Marks >45 C- - Marks > 40 D+ - Marks >35 D - Marks >30 I - Marks <30 If you entered, Marks = 100 Then the output should be like, Grade = A+
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