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Published byRudolph McLaughlin Modified over 9 years ago
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Introduction to Query Language and SQL
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Basic Query Language Operators Selection Projection Join Aggregates –Sum, Count, Max, Min, Avg SubTotal Calculated field
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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’);
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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 & "')"
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SQL Delete Command DELETE FROM tableName WHERE criteria; Ex 1. Delete a record from the Customer table. DELETE FROM CUSTOMER WHERE CID = ‘C1’;
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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 & "'"
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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
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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 & "'"
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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’;
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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
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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 & "‘”
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