11.11.2015 dat602 database application development lecture 3 review of sql language

DAT602 Database Application Development

Lecture 3 Review of SQL Language

• Structured Query LanguageDatabase computer language designed for managing data in relational database management systems (RMDBS).

Its scope includes data query and update, schema creation and modification, and data access control.

Database Application Development - Lecture 3

• Different database systems have different SQL languages. These SQL language are extensions of standard SQL language, they provide some additional support to the ANSI SQL-92 standard.

Microsoft SQL Server: Transact – SQLORACLE : Procedural Language/SQL (PL/SQL)


SQL language command• Create Table• Alter Table• Drop Table• Manipulate Table Data• Data Query


• Create TableThree aspects you should consider carefully before you create a table.- Data types. These include CHARACTER,INTEGER, FLOAT, and so on.- Data constraints. These include such restrictions as whether NULLS are permitted.- Default values. Default values can be assigned for each column.


• Command for creating a tableCREATE TABLE tableName

( column1Name dataType[(size)] [constraints] [default value],column2Name dataType[(size)] [constraints] [default value],column3Name dataType[(size)] [constraints] [default value],...);

CREATE TABLE CONTACT_INFO(CONTACT_ID INTEGERNOT NULL PRIMARY KEY,FIRST_NAME VARCHAR(20) NOT NULL,LAST_NAME VARCHAR(30) NOT NULL,STREET VARCHAR(50) NOT NULL);


• Alter Table : Add columnSometimes, after creating table, we need to alter table, like add, alter or remove a column.


Add

Syntax of Adding a column:AlTER TABLE TableName ADD newColumnName (size)Example:ALTER TABLE UserInfo ADD Gender char(1)

• Alter Table : remove column


remove

Syntax of removing a columnALTER TABLE TableName DROP COLUMN columnName;

Example:ALTER TABLE UserInfo DROP COLUMN Gender;

• Alter Table : alter column


alter

Syntax of alter column:ALTER TABLE TableName CHANGE OldColumnName

NewColumnName Type(Size);

Example:ALTER TABLE UserInfo CHANGE Age Gender

Char(1);

• Drop TableDelete existed table.Syntax of dropping table:DROP TABLE TableName;

Example:DROP TABLE UserInfo;


Data Manipulation• INSERT

Insert content into a table• UPDATE

Modify content of a table• DELETE

Delete content of a table


• INSERT


insert

Syntax of INSERT:INSERT INTO TableName (Column1, Column2, ...)

VALUES ( Value1, Value2, ...);

Example:INSERT INTO UserInfo (Name, Gender)

VALUES (‘Cindy’, ‘Female’);

Table: UserInfo

Table: UserInfo

• UPDATE: single row operation


update

Syntax of Update:UPDATE TableName SET Column1 = [NewValue]

WHERE {Condition}

Example:UPDATE UserInfo SET Gender = ‘Female’

WHERE Name = ‘Cindy’;

Table: UserInfo

Table: UserInfo

• UPDATE: multiple rows operation


update

Update:UPDATE Grade SET Grade = ‘A’

WHERE Gender= ‘Male’;

Table: Grade

Table: Grade

• DELETE operation


delete

Syntax of DELETE operation:DELETE FROM TableName

WHERE {Condition}

Example:DELETE FROM UserInfo WHERE Name = ‘Cindy’;

Table : UserInfo

Table : UserInfo

Data Query• Retrieve data from a database in response to

a query• Following part covers terms: SELECT, WHERE,

ORDER BY, DISTINCT, AND, OR


• The SELECT statement is the heart of a SQL query.Syntax of SELECT:SELECT Column1, Column2,.. FROM TableName


SELECT

Example:SELECT Name FROM UserInfo

• WHERE Clauseyou can restrict the query to return the requested fields from only records that match some specific criteria.

SELECT * FROM Table_Student WHERE Gender = ‘Male’


• Comparison operators- Equality (=)- Inequality (<>)- Greater Than (>) and Greater Than or Equal To (>=)- Less Than (<) and Less Than or Equal To (<=)- IS NULL- IS NOT NULL


• AND, ORYou can use AND, OR to combine multiple conditions to filter query result.

Syntax of AND, ORSELECT ColumnName FROM TableName WHERE Condition1 {[AND|OR] ConditionN } +


Example:SELECT store_name FROM Store_Information

WHERE Sales > 1000 OR (Sales < 500 AND Sales > 275)


• The DISTINCT keyword eliminates duplicate rows from the results of a SELECT statement.Syntax of DISTINCT:SELECT DISTINCT Column FROM Table

Example: SELECT DISTINCT Name FROM UserInfo


Table: UserInfo

SelectDistinct

result

• The ORDER BY clause sorts query results by one or more columns.Syntax of ORDER BY:SELECT Column1, Column2… FROM Table

ORDER BY ColumnN

A sort can be ascending (ASC) or descending (DESC). If neither is specified, ASC is assumed.


• Alias. We can give a simple, short table or column names to represent original long, complex names.

• Syntax of alias:SELECT “TableAlias”.”ColumnName“ “ColumnAlias” FROM “TableName” “TableAlias"

• Example of Alias:SELECT A1.UserFullName NameFROM UserInfo A1;


• Sort function is very useful for locating the maximal or minimal value.

• Example:SELECT * FROM UserInfo ORDER BY Age DESC


Table: UserInfo

Result set

SelectOrder

by

• Multiple table joint query.In well designed database, data in different tables are not overlapped.

• Most of time, the data we need is distributed in several different tables. So we need combine these related tables to do a joint query.


• Multiple tables joint query


Table: STUDENT_INFO

Table: GRADE_INFO

Get Anny’s grade:SELECT * FROM STUDENT_INFO s, GRADE_INFO g WHERE s.ID = g.ID AND s.Name = “Bob”

Query result

You can find more detail on following website:http://sql.1keydata.com/cn/


11.11.2015 dat602 database application development lecture 3 review of sql language

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