SQL COMMANDS

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SQL COMMANDS

• Insert, Update and the rest

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Lecture Objectives

• Utilize the standard query language (SQL) to
  perform the following tasks

• Add Rows to the Database
• Change Existing Rows in the Database
• Delete Rows from the Database
• Create, Alter and Remove Tables from the Database

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Insert Command

• Allows the insertion of data into a table one row
  at a time
• Used for new tables, or tables with existing data

• What about NULL values?

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Insert Command

• Alternate syntax

• When will Insert NOT Work?

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Update Command

• Modify an attribute of one or more rows in a
  given table

• When will Update NOT Work?

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Delete Command

• Removes rows from a single table

• Will delete ever remove from more than one table?

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Create Table Command

• Creates a new relation/table by giving the name,
  attributes and constraints on the table
• This is a water-downed version of the command

Name of New Table
Syntax CREATE TABLE lttbl_namegt (
column1 datatype constraint,
column2 datatype constraint, . . PRIMA
RY KEY (column1, column2, ) FOREIGN KEY
(column1, column2, ) REFERENCES
lttbl_name2gt)
Column Names
Set Primary and Foreign Keys
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Create Table Command

• Data types a few examples
• Numeric Data types NUMBER(I,D) INTEGER S
  MALLINT DECIMAL(I,D)
• Character Data types CHAR(L) VARCHAR(L)
• Date DATE

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Alter Table Command

• Change the table structure in a pre-existing table

• Note more options available for the alter command

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Drop Table Command

• Remove the table and its data from the database

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Examples