The SELECT ...
INTO form of SELECT
enables a query result to be stored in variables or written to a
file:
SELECT ... INTO
selects column
values and stores them into variables.
var_list
SELECT ... INTO OUTFILE writes the
selected rows to a file. Column and line terminators can be
specified to produce a specific output format.
SELECT ... INTO DUMPFILE writes a single
row to a file without any formatting.
The SELECT syntax description
(see Section 13.2.9, “SELECT Syntax”) shows the INTO
clause near the end of the statement. It is also possible to use
INTO immediately following the
select_expr list.
An INTO clause should not be used in a nested
SELECT because such a
SELECT must return its result to
the outer context.
The INTO clause can name a list of one or
more variables, which can be user-defined variables, stored
procedure or function parameters, or stored program local
variables. (Within a prepared SELECT ... INTO
OUTFILE statement, only user-defined variables are
permitted;see Section 13.6.4.2, “Local Variable Scope and Resolution”.)
The selected values are assigned to the variables. The number of
variables must match the number of columns. The query should
return a single row. If the query returns no rows, a warning
with error code 1329 occurs (No data), and
the variable values remain unchanged. If the query returns
multiple rows, error 1172 occurs (Result consisted of
more than one row). If it is possible that the
statement may retrieve multiple rows, you can use LIMIT
1 to limit the result set to a single row.
SELECT id, data INTO @x, @y FROM test.t1 LIMIT 1;
User variable names are not case sensitive. See Section 9.4, “User-Defined Variables”.
The SELECT ... INTO
OUTFILE ' form of
file_name'SELECT writes the selected rows
to a file. The file is created on the server host, so you must
have the FILE privilege to use
this syntax. file_name cannot be an
existing file, which among other things prevents files such as
/etc/passwd and database tables from being
destroyed. The
character_set_filesystem system
variable controls the interpretation of the file name.
The SELECT ... INTO
OUTFILE statement is intended primarily to let you
very quickly dump a table to a text file on the server machine.
If you want to create the resulting file on some other host than
the server host, you normally cannot use
SELECT ... INTO
OUTFILE since there is no way to write a path to the
file relative to the server host's file system.
However, if the MySQL client software is installed on the remote
machine, you can instead use a client command such as
mysql -e "SELECT ..." >
to generate the
file on the client host.
file_name
It is also possible to create the resulting file on a different host other than the server host, if the location of the file on the remote host can be accessed using a network-mapped path on the server's file system. In this case, the presence of mysql (or some other MySQL client program) is not required on the target host.
SELECT ... INTO
OUTFILE is the complement of
LOAD DATA
INFILE. Column values are written converted to the
character set specified in the CHARACTER SET
clause. If no such clause is present, values are dumped using
the binary character set. In effect, there is
no character set conversion. If a result set contains columns in
several character sets, the output data file will as well and
you may not be able to reload the file correctly.
The syntax for the export_options
part of the statement consists of the same
FIELDS and LINES clauses
that are used with the
LOAD DATA
INFILE statement. See Section 13.2.6, “LOAD DATA INFILE Syntax”, for
information about the FIELDS and
LINES clauses, including their default values
and permissible values.
FIELDS ESCAPED BY controls how to write
special characters. If the FIELDS ESCAPED BY
character is not empty, it is used when necessary to avoid
ambiguity as a prefix that precedes following characters on
output:
The FIELDS ESCAPED BY character
The FIELDS [OPTIONALLY] ENCLOSED BY
character
The first character of the FIELDS TERMINATED
BY and LINES TERMINATED BY
values
ASCII NUL (the zero-valued byte; what is
actually written following the escape character is ASCII
0, not a zero-valued byte)
The FIELDS TERMINATED BY, ENCLOSED
BY, ESCAPED BY, or LINES
TERMINATED BY characters must be
escaped so that you can read the file back in reliably. ASCII
NUL is escaped to make it easier to view with
some pagers.
The resulting file does not have to conform to SQL syntax, so nothing else need be escaped.
If the FIELDS ESCAPED BY character is empty,
no characters are escaped and NULL is output
as NULL, not \N. It is
probably not a good idea to specify an empty escape character,
particularly if field values in your data contain any of the
characters in the list just given.
Here is an example that produces a file in the comma-separated values (CSV) format used by many programs:
SELECT a,b,a+b INTO OUTFILE '/tmp/result.txt' FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"' LINES TERMINATED BY '\n' FROM test_table;
If you use INTO DUMPFILE instead of
INTO OUTFILE, MySQL writes only one row into
the file, without any column or line termination and without
performing any escape processing. This is useful if you want to
store a BLOB value in a file.
Any file created by INTO OUTFILE or
INTO DUMPFILE is writable by all users on
the server host. The reason for this is that the MySQL server
cannot create a file that is owned by anyone other than the
user under whose account it is running. (You should
never run mysqld as
root for this and other reasons.) The file
thus must be world-writable so that you can manipulate its
contents.
If the secure_file_priv
system variable is set to a nonempty directory name, the file
to be written must be located in that directory.
In the context of
SELECT ...
INTO statements that occur as part of events executed
by the Event Scheduler, diagnostics messages (not only errors,
but also warnings) are written to the error log, and, on
Windows, to the application event log. For additional
information, see Section 20.4.5, “Event Scheduler Status”.