MySQL 5.6 Reference Manual Including MySQL NDB Cluster 7.3-7.4 Reference Guide

13.2.9.1 SELECT ... INTO Statement

The SELECT ... INTO form of SELECT enables a query result to be stored in variables or written to a file:

A given SELECT statement can contain at most one INTO clause, although as shown by the SELECT syntax description (see Section 13.2.9, “SELECT Statement”), the INTO can appear in different positions:

An INTO clause should not be used in a nested SELECT because such a SELECT must return its result to the outer context. There are also constraints on the use of INTO within UNION statements; see Section 13.2.9.3, “UNION Clause”.

For the INTO var_list variant:

User variable names are not case-sensitive. See Section 9.4, “User-Defined Variables”.

The SELECT ... INTO OUTFILE 'file_name' form of 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 modified. The character_set_filesystem system variable controls the interpretation of the file name.

The SELECT ... INTO OUTFILE statement is intended to enable dumping a table to a text file on the server host. To create the resulting file on some other host, SELECT ... INTO OUTFILE normally is unsuitable because there is no way to write a path to the file relative to the server host file system, unless the location of the file on the remote host can be accessed using a network-mapped path on the server host file system.

Alternatively, if the MySQL client software is installed on the remote host, you can use a client command such as mysql -e "SELECT ..." > file_name to generate the file on that host.

SELECT ... INTO OUTFILE is the complement of LOAD DATA. 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, so will the output data file and it may not be possible 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 statement. For information about the FIELDS and LINES clauses, including their default values and permissible values, see Section 13.2.6, “LOAD DATA Statement”.

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 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 need not 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 for selecting a BLOB value and storing it in a file.

Note

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”.