Introduction to Query Language and SQL

Basic Query Language Operators

• Selection

• Projection

• Join

• Aggregates– Sum, Count, Max, Min, Avg

• SubTotal

• Calculated field

SQL Insert CommandINSERT INTO tableName VALUES (field values separated by commas);

INSERT INTO tableName (Column names separated by commas)VALUES (field values separated by commas);

Ex 1. Customer table with CID, CNAME, CITY, RATING.

a. INSERT INTO CUSTOMER VALUES (‘C1’, ‘SMITH’, ‘SF’, ‘A’);

b. INSERT INTO CUSTOMER (CID, CNAME,RATING) VALUES (‘C1’, ‘SMITH’, ‘A’);

Ex 2. Orders table with OID, OrderDate, CID, SalesPerson

INSERT INTO ORDERS VALUES (‘O11’, #9/28/02#, ‘C1’, ‘Peter’);

Creating A String Containing SQL Insert Command

Assuming the four fields of the new customer record are entered in textboxes:

Dim strSQLInsert As String

strSQLInsert = "Insert into Customer values ('"

strSQLInsert = strSQLInsert & TextBox1.Text & "','" & TextBox2.Text & "','"

strSQLInsert = strSQLInsert & TextBox3.Text & "','" & TextBox4.Text & "')"

SQL Delete Command

DELETE FROM tableName WHERE criteria;

Ex 1. Delete a record from the Customer table.

DELETE FROM CUSTOMER WHERE CID = ‘C1’;

Creating A String Containing SQL Delete Command

Assuming the deleted record’s ID is selected from a list box:

Dim strSQLDel As String = “DELETE FROM CUSTOMER WHERE CID = ‘“

strSQLDel = strSQLDel & ListBox1.SelectedItem & "'"

SQL Update Command

UPDATE tableName SET field = new value WHERE criteria;

Ex.

1. UPDATE CUSTOMER SET RATING = ‘A’ WHERE CID=‘C1’;

2. UPDATE EMPLOYEE SET SALARY = SALARY*1.05

Creating A String Containing SQL Update Command

Assuming the CID is selected from a list box, and the new rating is entered in a text box:

Dim strSQLUpd As String = "Update customer set rating = '" & textbox1.text & "'"

strSQLUpd = strSQLUpd & " where cid='" & ListBox1.SelectedItem & "'"

SQL Select Command

1. SELECT * FROM tableName WHERE criteria;

Ex. SELECT * FROM CUSTOMER WHERE RATING = ‘a’;

2. SELECT fields FROM tableName WHERE criteria;

Ex. SELECT CID, CNAME, RATING FROM EMPLOYEE

WHERE CITY = ‘sf’;

Aggregates1. SELECT COUNT(CID) AS custCount FROM

CUSTOMER;

2. SELECT COUNT(EID) AS empCount, SUM(SALARY) AS totalSalary, AVG(SALARY) AS avgSalary FROM EMPLOYEE;

3. Group By:

Ex. SELECT CITY, COUNT(CID) As CustCount FROM

CUSTOMER GROUP BY CITY;

Ex. SELECT SEX, AVG(SALARY) AS avgSalary FROM

EMPLOYEE GROUP BY SEX;

Note: Alias CustCount

Creating A String Containing SQL Select Command

•Assuming the rating is selected from a list box:

•dim strSQL as string = "select * from customer where rating = ‘“•strSQL = strSQL & ListBox1.SelectedItem & "‘”