Entering Queries
195
+----------------+--------------+
| VERSION() | CURRENT_DATE |
+----------------+--------------+
| 5.0.7-beta-Max | 2005-07-11 |
+----------------+--------------+
1 row in set (0.01 sec)
mysql>
This query illustrates several things about
mysql
:
• A command normally consists of an SQL statement followed by a semicolon. (There are some
exceptions where a semicolon may be omitted.
QUIT
, mentioned earlier, is one of them. We'll get to
others later.)
• When you issue a command,
mysql
sends it to the server for execution and displays the results,
then prints another
mysql>
prompt to indicate that it is ready for another command.
•
mysql
displays query output in tabular form (rows and columns). The first row contains labels for
the columns. The rows following are the query results. Normally, column labels are the names of the
columns you fetch from database tables. If you're retrieving the value of an expression rather than a
table column (as in the example just shown),
mysql
labels the column using the expression itself.
•
mysql
shows how many rows were returned and how long the query took to execute, which gives
you a rough idea of server performance. These values are imprecise because they represent wall
clock time (not CPU or machine time), and because they are affected by factors such as server load
and network latency. (For brevity, the “rows in set” line is sometimes not shown in the remaining
examples in this chapter.)
Keywords may be entered in any lettercase. The following queries are equivalent:
mysql>
SELECT VERSION(), CURRENT_DATE;
mysql>
select version(), current_date;
mysql>
SeLeCt vErSiOn(), current_DATE;
Here is another query. It demonstrates that you can use
mysql
as a simple calculator:
mysql>
SELECT SIN(PI()/4), (4+1)*5;
+------------------+---------+
| SIN(PI()/4) | (4+1)*5 |
+------------------+---------+
| 0.70710678118655 | 25 |
+------------------+---------+
1 row in set (0.02 sec)
The queries shown thus far have been relatively short, single-line statements. You can even enter
multiple statements on a single line. Just end each one with a semicolon:
mysql>
SELECT VERSION(); SELECT NOW();
+----------------+
| VERSION() |
+----------------+
| 5.0.7-beta-Max |
+----------------+
1 row in set (0.00 sec)
+---------------------+
| NOW() |
+---------------------+
| 2005-07-11 17:59:36 |
+---------------------+
1 row in set (0.00 sec)
A command need not be given all on a single line, so lengthy commands that require several lines are
not a problem.
mysql
determines where your statement ends by looking for the terminating semicolon,
not by looking for the end of the input line. (In other words,
mysql
accepts free-format input: it collects
input lines but does not execute them until it sees the semicolon.)
Summary of Contents for 5.0
Page 1: ...MySQL 5 0 Reference Manual ...
Page 18: ...xviii ...
Page 60: ...40 ...
Page 396: ...376 ...
Page 578: ...558 ...
Page 636: ...616 ...
Page 844: ...824 ...
Page 1234: ...1214 ...
Page 1427: ...MySQL Proxy Scripting 1407 ...
Page 1734: ...1714 ...
Page 1752: ...1732 ...
Page 1783: ...Configuring Connector ODBC 1763 ...
Page 1793: ...Connector ODBC Examples 1773 ...
Page 1839: ...Connector Net Installation 1819 2 You must choose the type of installation to perform ...
Page 2850: ...2830 ...
Page 2854: ...2834 ...
Page 2928: ...2908 ...
Page 3000: ...2980 ...
Page 3122: ...3102 ...
Page 3126: ...3106 ...
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