Concept explainers
“SELECT” command:
The “SELECT” command is used to retrieve data in a
Syntax for selecting values from the table is as follows:
SELECT STUDENT_ID FROM STUDENT;
- The given query is used to display each student ID from “STUDENT” table.
“SUM” function:
- It is the one function of aggregate function.
- The “SUM” function is used to compute the total of the values in a column.
Example:
The example for “SUM” function is given below:
SELECT SUM(MARK_CREDIT) FROM STUDENT;
The above query is used to display the sum of all students mark credit from “STUDENT” table using “SUM” function.
“GROUP BY” Clause:
- User can group the data using “GROUP BY” clause.
- This clause allows the user to group data on a specific column and then computes statistics when user preferred.
Example:
The example for “GROUP BY” clause is given below:
SELECT CUSTOMER_NAME, SUM(AMOUNT) FROM CUSTOMERS GROUP BY CUSTOMER_NAME;
The above query is used to list the customer name and the sum of amount using “GROUP BY” clause.
“HAVING” Clause:
- The “HAVING” clause is used to restrict the groups that are included.
- This restriction does not apply to individual rows but relatively apply to groups.
Example:
The example for “HAVING” clause is given below:
SELECT STUDENT_ID, NAME, AGE, ADDRESS, TOTAL_MARK FROM STUDENTS GROUP BY AGE HAVING COUNT(AGE) >= 10;
- The above query is used to display a record for a similar age count that would be more than or equal to “10”.
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Chapter 4 Solutions
A Guide to SQL
- A Guide to SQLComputer ScienceISBN:9781111527273Author:Philip J. PrattPublisher:Course Technology Ptr