Introduction to Query Language and SQL

Basic Query Language Operators Selection Projection Join Aggregates –Sum, Count, Max, Min, Avg SubTotal Calculated field

SQL Insert Command INSERT 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’;

Aggregates 1.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 CUSTOMERGROUP 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 & "‘”