Dbms Commands

8/3/2019 Dbms Commands

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CREATE TABLE - SQL Command

CREATE TABLE student (StudentID varchar(6), StudentName Character(20), Age int(2), Dept varchar(20));

SQL Insert Query:

INSERT INTO student (StudentID,StudentName,Age,Dept)VALUES('y7cs201','abcd',19,'cse');

SQL Select Query:

SELECT table_column1, table_column2, table_column3 FROM tablename;

Select * from student;

Select StudentID from student;

SQL - Update

The update clause updates column values of a table. Update requires a conditional statement to select the row

be updated

UPDATE student SET StudentName = 'Fletcher' WHERE StudentID = 'y7cs201';

SQL - Alter Table

The alter clause changes a table by adding, removing, or modifying an existing table column.

ALTER TABLE student ADD dob varchar(10);

SQL - Delete

Entire rows can be deleted from a table using the delete clause.

DELETE FROM student WHERE StudentID='y6cs203';

SQL - Order By

The order by statement allows for table column assortment. It allows for ascending or descending lists of yo

table column values permitting SQL to reorder your table rows for the purpose of viewing.

SELECT * FROM student ORDER BY StudentName;

SELECT * FROM student ORDER BY Age,StudentName;


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SQL - Distinct Usage

Distinct is used to retrieve rows of your database that have unique values for a given column. For example say w

have a table of employees and in this table of employees we have several job titles from janitors to CEOs. W

would like to know just how many distinct job titles we have.

SELECT DISTINCT job_titles FROM student;

The AND & OR Operators

The AND operator displays a record if both the first condition and the second condition is true.

The OR operator displays a record if either the first condition or the second condition is true.

SELECT * FROM Persons WHERE FirstName='Tove' AND LastName='Svendson'

SELECT * FROM Persons WHERE FirstName='Tove' OR FirstName='Ola'

SELECT * FROM Persons WHERE LastName='Svendson' AND (FirstName='Tove' OR FirstName='Ola

The ORDER BY Keyword

The ORDER BY keyword is used to sort the result-set by a specified column.

The ORDER BY keyword sort the records in ascending order by default.

If you want to sort the records in a descending order, you can use the DESC keyword.

SQL ORDER BY Syntax

SELECT column_name(s)

FROM table_name

ORDER BY column_name(s) ASC|DESC

SELECT * FROM Persons ORDER BY LastName

SELECT * FROM Persons ORDER BY LastName DESC

The TOP Clause

The TOP clause is used to specify the number of records to return.

The TOP clause can be very useful on large tables with thousands of records. Returning a largnumber of records can impact on performance.

Note: Not all database systems support the TOP clause.


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SQL Server Syntax

SELECT TOP number|percent column_name(s)

FROM table_name

MySQL Syntax


FROM table_name

LIMIT number

SELECT * FROM Persons LIMIT 5SELECT column_name(s) FROM table_name WHERE ROWNUM


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SELECT * FROM Persons WHERE City LIKE 's%'

The "%" sign can be used to define wildcards (missing letters in the pattern) both before and aftthe pattern.

SELECT * FROM Persons WHERE City LIKE '%s'

SELECT * FROM Persons WHERE City LIKE '%tav%'

SELECT * FROM Persons WHERE City NOT LIKE '%tav%'

The IN Operator

The IN operator allows you to specify multiple values in a WHERE clause.

SQL IN Syntax


FROM table_name

WHERE column_name IN (value1,value2,...)

SELECT * FROM Persons WHERE LastName IN ('Hansen','Pettersen')

The BETWEEN operator is used in a WHERE clause to select a range of data between two values.

The BETWEEN Operator

The BETWEEN operator selects a range of data between two values. The values can be numbetext, or dates.

SQL BETWEEN Syntax


FROM table_name

WHERE column_name

BETWEEN value1 AND value2

Now we want to select the persons with a last name alphabetically between "Hansen" a"Pettersen" from the table above.

We use the following SELECT statement:

SELECT * FROM Persons WHERE LastName BETWEEN 'Hansen' AND 'Pettersen'


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MySQL Date Functions

The following table lists the most important built-in date functions in MySQL:

Function Description

NOW() Returns the current date and time

CURDATE() Returns the current date

CURTIME() Returns the current time

DATE() Extracts the date part of a date or date/time expression

EXTRACT() Returns a single part of a date/time

DATE_ADD() Adds a specified time interval to a date

DATE_SUB() Subtracts a specified time interval from a date

DATEDIFF() Returns the number of days between two datesDATE_FORMAT() Displays date/time data in different formats

SQL Server Date Functions

The following table lists the most important built-in date functions in SQL Server:

Function Description

GETDATE() Returns the current date and time

DATEPART() Returns a single part of a date/time

DATEADD() Adds or subtracts a specified time interval from a date

DATEDIFF() Returns the time between two dates

CONVERT() Displays date/time data in different formats

SQL Date Data Types

MySQL comes with the following data types for storing a date or a date/time value in the database:

DATE - format YYYY-MM-DD

DATETIME - format: YYYY-MM-DD HH:MM:SS

TIMESTAMP - format: YYYY-MM-DD HH:MM:SS

YEAR - format YYYY or YY

SQL Server comes with the following data types for storing a date or a date/time value in thdatabase:


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DATE - format YYYY-MM-DD

DATETIME - format: YYYY-MM-DD HH:MM:SS

SMALLDATETIME - format: YYYY-MM-DD HH:MM:SS

TIMESTAMP - format: a unique number

Now we want to select the records with an OrderDate of "2008-11-11" from the table above.

We use the following SELECT statement:

SELECT * FROM Orders WHERE OrderDate='2008-11-11'

SELECT * FROM Orders WHERE OrderDate='2008-11-11'

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Dbms Commands