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 & "‘”
Top Related