CREATE TABLE is used to create tables in a database. The CREATE TABLE statement must specify the table name and include a list of fields defined by name and data type. Data types can be predefined types like INT for numbers or VARCHAR for variable-width character strings. The example shows a CREATE TABLE statement that defines a Students table with three fields: StudentID as a fixed-width CHAR, and LastName and FirstName as variable-width VARCHAR fields.

1. Data Definition Language
CIS-182

2. DDL
• Data Definition Language: Work with Objects
– Objects are Database, Tables
• Three commands for objects
– Create an object
– Alter an object
– Delete an object
– Follow command with type then name
• CREATE TABLE Students

3. Database
• Must create container first
– Not all vendors use databases, may be defined as a
SCHEMA
• Optional Parameters depend on vendor
– Parameter is a value passed to a command
• Similar to an argument in other languages
– Can create database without optional parameters
3

4. CREATE SQL SERVER DATABASE
• Must have name
• Can specify filenames and locations
– SQL Server uses two files
• Data file (.mdf) to store objects and data
• Log file (.ldf) to track actions applied to database
– Can specify file characteristics, such as growth
– Files can be organized into groups
• Have at least one file group
• Aid to manage across machines

5. MS CREATE DATABASE
CREATE DATABASE database_name
[ ON
[ < filespec > [ ,...n ] ]
[ , < filegroup > [ ,...n ] ]
]
[ LOG ON { < filespec > [ ,...n ] } ]
[ COLLATE collation_name ]
[ FOR LOAD | FOR ATTACH ]

6. Placeholder Definitions
< filespec > ::=
[ PRIMARY ]
( [ NAME = logical_file_name , ]
FILENAME = 'os_file_name'
[ , SIZE = size ]
[ , MAXSIZE = { max_size | UNLIMITED } ]
[ , FILEGROWTH = growth_increment ] )
[ ,...n ]
< filegroup > ::=
FILEGROUP filegroup_name < filespec > [ ,...n ]

7. Create Table
• Table must include a field list
– At least one field
– List values are separated by comma
– List begin/end defined by parentheses
• Persistent v. Temporary
– Persistent tables store data even when not in use
– Temporary tables have data available at certain times
• Usually used in stored procedures, reporting

8. Fields
• Field must have a name and datatype
– Datatype can be predefined, user defined or
constructed
– Sample Predefined (built-in) datatypes:
• CHAR
• INT
• SMALLDATETIME
• See Books Online for complete list

9. String Datatypes
• Strings datatypes store any character
• Should field be fixed-width?
– CHAR is fixed width, if a value is shorter than field
size the remaining positions will have spaces entered
– VARCHAR is variable width, only the value is stored
to the maximum number of characters

10. Unicode/National Character Set
• Do text values include characters other than
those typically found in English words?
– “N” stands for National Character Set
– Each character takes twice as much storage
– CHAR v. NCHAR
• Char: Fixed width field for storing “standard” characters
• NCHAR: Fixed width field for storing characters from any
language
– Also have NVARCHAR for varying-width fields

11. Number Datatypes
• Use the following questions to determine the
datatype needed for numeric fields
– Does a field store a whole number or fraction (or
exponent)?
• Whole number datatypes include INT, SMALLINT
• Fractions include DECIMAL, REAL
– Exact or approximate?
• SMALLINT, INT store actual values
• FLOAT, REAL store approximate values
– What are the largest/smallest values?
• INT stores a larger value than SMALLINT

12. Create Table Example
CREATE TABLE Students
(StudentID CHAR(9),
LastName VARCHAR(35),
FirstName VARCHAR(25))
• Table name is Students
• Fields are a list (enclosed in parentheses)
– Student ID is a fixed-width field with 9 spaces
– Last name is a variable-width field with space for up
to 35 characters