Database Reference
In-Depth Information
CHAPTER 3
Selecting Data from Tables
3.0. Introduction
This chapter focuses on using the
SELECT
statement to retrieve information from your
database. You will find the chapter helpful if your SQL background is limited or to find
out about the MySQL-specific extensions to
SELECT
syntax.
There are many ways to write
SELECT
statements; we'll look at only a few. Consult the
MySQL Reference Manual
or a general MySQL text for more information about
SE
LECT
syntax and the functions and operators available to extract and manipulate data.
Many examples in this chapter use a table named
mail
that contains rows that track
mail message traffic between users on a set of hosts:
CREATE
TABLE
mail
(
t
DATETIME
,
#
when
message
was
sent
srcuser
VARCHAR
(
8
),
#
sender
(
source
user
and
host
)
srchost
VARCHAR
(
20
),
dstuser
VARCHAR
(
8
),
#
recipient
(
destination
user
and
host
)
dsthost
VARCHAR
(
20
),
size
BIGINT
,
#
message
size
in
bytes
INDEX
(
t
)
);
The
mail
table contents look like this:
mysql>
SELECT * FROM mail;
+---------------------+---------+---------+---------+---------+---------+
| t | srcuser | srchost | dstuser | dsthost | size |
+---------------------+---------+---------+---------+---------+---------+
| 2014-05-11 10:15:08 | barb | saturn | tricia | mars | 58274 |
| 2014-05-12 12:48:13 | tricia | mars | gene | venus | 194925 |
| 2014-05-12 15:02:49 | phil | mars | phil | saturn | 1048 |
| 2014-05-12 18:59:18 | barb | saturn | tricia | venus | 271 |
