1. Insert, Update and the rest…
SQL COMMANDS
Insert, Update and the rest…

2. 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

3. Insert Command What about NULL values?
Allows the insertion of data into a table one row at a time
Used for new tables, or tables with existing data
Syntax 1:
INSERT INTO <tbl_name> VALUES (attrib_value1, attrib_value2,…)
Values for all attributes in the table
Name of the table
What about NULL values?
Syntax 2:
INSERT INTO <tbl_name> VALUES (attrib_value1, attrib_value2, NULL, …)
Column cannot be specified as not null

4. Insert Command Alternate syntax When will Insert NOT Work? Syntax 3:
INSERT INTO <tbl_name>(col1, col2, …) VALUES (attrib_value1, attrib_value2,…)
All other columns will be inserted as null or their default value
Does not need to be all columns, just those columns specified as not null with no default value
When will Insert NOT Work?

5. Update Command
Modify an attribute of one or more rows in a given table
Syntax:
UPDATE <tbl_name>
SET columnname = value [, columnname=value,..]
[WHERE CLAUSE]
One or more changes to attributes
Where clause acts just like a select where clause with =, LIKE, sub-queries etc.
When will Update NOT Work?

6. Delete Command Removes rows from a single table
Syntax:
DELETE FROM <tbl_name>
[WHERE CLAUSE]
Table name to delete rows from
Where clause acts just like a select where clause with =, LIKE, sub-queries etc.
Will delete ever remove from more than one table?

7. 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 <tbl_name> (
column1 datatype [constraint],
column2 datatype [constraint], .
PRIMARY KEY (column1, column2, …)
FOREIGN KEY (column1, column2, …) REFERENCES <tbl_name2>)
Column Names
Set Primary and Foreign Keys

8. Create Table Command Data types – a few examples
Numeric Data types NUMBER(I,D) INTEGER SMALLINT DECIMAL(I,D)
Character Data types CHAR(L) VARCHAR(L)
Date DATE

9. Alter Table Command Change the table structure in a pre-existing table
Syntax 1: ALTER TABLE <tbl_name> [ADD|MODIFY] (columnname datatype)
Syntax 2: ALTER TABLE <tbl_name>
DROP COLUMN <column_name>
Table name to Alter
Remove a Column from the table
Add or Change Column Settings
Note: more options available for the alter command

10. Drop Table Command Remove the table and its data from the database
Syntax:
DROP TABLE <tbl_name>
Table name to remove from the database

11. Examples