sundara ram matta [email protected] apr 01 st, 2015 - sundara ram matta...
TRANSCRIPT
IMPORTANT ANNOUNCEMENTS !!!
• HW #4 due by this Friday – 4/3/2015
• HW #5 has been posted and due date is next Friday – 4/10/2015.
• Also MyITLab Lesson D – due by Monday 4/6/2015.
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INTRODUCTION
• SQL is short for Structured Query Language.
• SQL is pronounced “sequel”.
• It is a widely used database language, providing means of data manipulation (store, retrieve, update, delete) and database creation.
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INTRODUCTION
• Almost all modern RDMS use SQL as standard database language.
– MS SQL Server– Microsoft Access– Oracle– Sybase– Informix
• Although all those RDBMS use SQL, they use different SQL dialects.
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SQL DATABASE TABLE
• The foundation of every RDMS is a database object called TABLE.
• The database table columns (called also table fields) have their own unique names and have a pre-defined data types.
• While table columns describe the data types, the table rows contain the actual data for the columns.
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SQL DATABASE TABLE
CustomerID CustomerName ContactName Address City PostalCode Country
1 Alfreds Futterkiste Maria Anders Obere Str. 57 Berlin 12209 Germany
2Ana Trujillo
Emparedados y helados
Ana TrujilloAvda. de la
Constitución 2222México D.F. 5021 Mexico
3Antonio Moreno
TaqueríaAntonio Moreno Mataderos 2312 México D.F. 5023 Mexico
4 Around the Horn Thomas Hardy 120 Hanover Sq. London WA1 1DP UK
5 Berglunds snabbköp Christina Berglund Berguvsvägen 8 Luleå S-958 22 Sweden
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SQL INSTRUCTIONS
Keep in Mind That...• SQL is NOT case sensitive: select is the
same as SELECT
Semicolon after SQL Statements?• Semicolon is the standard way to separate each
SQL statement in database systesm.
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MOST IMPORTANT SQL COMMANDS
• SELECT - extracts data from a database• UPDATE - updates data in a database• DELETE - deletes data from a database• INSERT INTO - inserts new data into a database• CREATE DATABASE - creates a new database• ALTER DATABASE - modifies a database• CREATE TABLE - creates a new table• ALTER TABLE - modifies a table• DROP TABLE - deletes a table• CREATE INDEX - creates an index (search key)• DROP INDEX - deletes an index
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SQL SELECT STATEMENT
• The SELECT statement is used to select data from a database.
• The result is stored in a result table, called the result-set.
• SELECT column_name,column_nameFROM table_name;
• SELECT * FROM table_name;
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SQL SELECT ‘DISTINCT’ STATEMENT
• In a table, a column may contain many duplicate values; and sometimes you only want to list the different (distinct) values.
• The DISTINCT keyword can be used to return only distinct (different) values.
• SELECT DISTINCT column_name,column_nameFROM table_name;
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SQL WHERE CLAUSE
• The WHERE clause is used to extract only those records that fulfil a specified criterion.
• SELECT column_name,column_nameFROM table_nameWHERE column_name operator value;
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SQL WHERE CLAUSE
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Operator Description
= Equal
<> Not equal. Note: In some versions of SQL this operator may be written as !=
> Greater than
< Less than
>= Greater than or equal
<= Less than or equal
BETWEEN Between an inclusive range
LIKE Search for a pattern
IN To specify multiple possible values for a column
SQL AND & OR OPERATORS
• The AND & OR operators are used to filter records based on more than one condition.
• The AND operator displays a record if both the first condition AND the second condition are true.
• The OR operator displays a record if either the first condition OR the second condition is true.
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SQL UPDATE STATEMENT
• The UPDATE statement is used to update records in a table.
• UPDATE table_nameSET column1=value1,column2=value2,...WHERE some_column=some_value;
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SQL UPDATE STATEMENT
• Be careful when updating records. If we had omitted the WHERE clause, in the example above, like this:
• UPDATE CustomersSET ContactName='Alfred Schmidt', City='Hamburg';
• Entire ContactName and City Column will get replaced.
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SQL DELETE STATEMENT
• The DELETE statement is used to delete records in a table.
• DELETE FROM table_nameWHERE some_column=some_value;
• Notice the WHERE clause in the SQL DELETE statement!
• Be very careful when deleting records. You cannot undo this statement!
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SQL ORDER BY KEYWORD
• The ORDER BY keyword is used to sort the result-set by one or more columns.
• The ORDER BY keyword sorts the records in ascending order by default.
• SELECT column_name, column_nameFROM table_nameORDER BY column_name DESC, column_name DESC;
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SQL ’JOIN’ KEYWORD
• An SQL JOIN clause is used to combine rows from two or more tables, based on a common field between them.
• The most common type of join is: SQL INNER JOIN (simple join).
• An SQL INNER JOIN return all rows when there is at least one match in BOTH the tables.
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NEXT WEEK…
• Study the Reports – just like forms, Cover Misc. topics and we will wrap up MS - Access.
• We will have an Exam review session on Wednesday – April 08th.
• Exam #2: Comprehensive on MS Access
Monday – April 13th (Section 3).
Wednesday – April 15th (Section 5).
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