Page 4 - Simple Queries in SQL

TEXT Values are treated as TINYTEXT Maximum length of 255 characters.
character strings having TEXT Maximum length of 65535
a character set. characters.
MEDIUMTEXT Maximum length of 16777215
characters.
LONGTEXT Maximum length of 4294967295
characters

ENUM Types
A string object whose value is chosen from a list of values given at the time of table creation. For
example -
CREATE TABLE length ( length ENUM('small', 'medium', 'large') );
and only those values (or NULL) could ever populate that field, enum values should be string in single
quote.

SET Types
A string object having zero or more comma separated values (maximum 64). Values are chosen from
a list of values given at the time of table creation.

CHAR vs VARCHAR
CHAR VARCHAR
Used to store character string value Used to store variable length alphanumeric data.
of fixed length.
It can hold a maximum of 255 characters. It can hold a maximum of 65,535 characters.
It's 50% faster than VARCHAR. It's slower than CHAR.
It uses static memory allocation. It uses dynamic memory allocation

NULL value
• No value in a cell is NULL/null value.
• Its not equal to zero(ZERO ≠ NULL)
• Any arithmetic expression containing a NULL always evaluates to NULL.
• When displaying the content of a table if a cell contain null value MySQL display it as NULL.

SQL operators
Relational Operators are:
<, <=, >, >=, =, != (<>)
Logical operators are:
AND (&&), OR (II), NOT(!)

SELECT Statement Basics

The SQL SELECT statement queries data from tables in the database. The statement begins with the
SELECT keyword. The basic SELECT statement has 3 clauses:
• SELECT
• FROM
• WHERE
General format is:
select <col1>, <col2>,…………,<col n>
from <table1>, <table2>
where <condition>