Creating Database Tables

After the database structure is designed and the database has been created, individual tables can be added. Using accurate assignment of data types and their associated options, tables can be added to the database.

The command syntax is shown below, including the various column and table options;

CREATE TABLE <table> ( <column name> <column type> [<column options>],[<column name> <column type> [<column options>],…,] [<index list>])[<table options> ];

Example:

mysql> CREATE TABLE CountryLanguage (
         -> CountryCode CHAR(3) NOT NULL,
         -> Language CHAR(30) NOT NULL,
         -> IsOfficial ENUM('True', 'False') NOT NULL DEFAULT 'False',
         -> Percentage FLOAT(3,1) NOT NULL,
         -> PRIMARY KEY(Country, Language)
         -> )ENGINE = MyISAM COMMENT='Lists Language Spoken';

A line-by-line description of the above CREATE TABLE statement:

1. The table being created will be given the name CountryLanguage - this is the beginning of a grouping of column definitions that ends on the line 7 beginning with ") ENGINE = ..."

2. CountryCode --column in the table with a datatype of Char (size of 3) that cannot have an unknown or NULL value, and the comma ( ,) means continue defining columns

3. Language--another column of a datatype CHAR and a length of 30 that also can not have an unknown or NULL value

4. IsOfficial --column name ENUM is a datatype with only the values of True or False ('True' , 'False') and NOT NULL means each row must be true or false no t (unknown) If the value is unknown it will list as false by the phrase DEFAULT 'False'

5. Percentage —column with a datatype of FLOAT and values assigned at 3 total digits with 1 digit to the right of the decimal, cannot have NULL values

6. PRIMARY KEY--defines the type of index and what columns it applies, in this case a combo of both Country and Language to define a uniq ue identifier of each row or each entity

7. ) is the closing of a group of definitions describing the column names and index, ENGINE defines the pluggable storage engine used to manage the data and retrieve the data. (MyISAM in this case), COMMENT is phrases used by the person defining the table to explain the table (the purpose is to list the languages used in each given country), the ; means execute this command and create the table CountryLanguage.

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