root@localhost[lhrdb]> help load data
Name: 'LOAD DATA'
Description:
Syntax:
LOAD DATA [LOW_PRIORITY | CONCURRENT] [LOCAL] INFILE 'file_name'
[REPLACE | IGNORE]
INTO TABLE tbl_name
[PARTITION (partition_name,...)]
[CHARACTER SET charset_name]
[{FIELDS | COLUMNS}
[TERMINATED BY 'string']
[[OPTIONALLY] ENCLOSED BY 'char']
[ESCAPED BY 'char']
]
[LINES
[STARTING BY 'string']
[TERMINATED BY 'string']
]
[IGNORE number {LINES | ROWS}]
[(col_name_or_user_var,...)]
[SET col_name = expr,...]
The LOAD DATA INFILE statement reads rows from a text file into a table
at a very high speed. LOAD DATA INFILE is the complement of SELECT ...
INTO OUTFILE. (See
http://dev.MySQL.com/doc/refman/5.7/en/select-into.html.) To write data
from a table to a file, use SELECT ... INTO OUTFILE. To read the file
back into a table, use LOAD DATA INFILE. The syntax of the FIELDS and
LINES clauses is the same for both statements. Both clauses are
optional, but FIELDS must precede LINES if both are specified.
You can also load data files by using the mysqlimport utility; it
operates by sending a LOAD DATA INFILE statement to the server. The
--local option causes mysqlimport to read data files from the client
host. You can specify the --compress option to get better performance
over slow networks if the client and server support the compressed
protocol. See http://dev.mysql.com/doc/refman/5.7/en/mysqlimport.html.
For more information about the efficiency of INSERT versus LOAD DATA
INFILE and speeding up LOAD DATA INFILE, see
http://dev.mysql.com/doc/refman/5.7/en/insert-optimization.html.
The file name must be given as a literal string. On Windows, specify
backslashes in path names as forward slashes or doubled backslashes.
The character_set_filesystem system variable controls the
interpretation of the file name.
LOAD DATA supports explicit partition selection using the PARTITION
option with a comma-separated list of one or more names of partitions,
subpartitions, or both. When this option is used, if any rows from the
file cannot be inserted into any of the partitions or subpartitions
named in the list, the statement fails with the error Found a row not
matching the given partition set. For more information, see
http://dev.mysql.com/doc/refman/5.7/en/partitioning-selection.html.
For partitioned tables using storage engines that employ table locks,
such as MyISAM, LOAD DATA cannot prune any partition locks. This does
not apply to tables using storage engines which employ row-level
locking, such as InnoDB. For more information, see
http://dev.mysql.com/doc/refman/5.7/en/partitioning-limitations-locking
.html.
The server uses the character set indicated by the
character_set_database system variable to interpret the information in
the file. SET NAMES and the setting of character_set_client do not
affect interpretation of input. If the contents of the input file use a
character set that differs from the default, it is usually preferable
to specify the character set of the file by using the CHARACTER SET
clause. A character set of binary specifies "no conversion."
LOAD DATA INFILE interprets all fields in the file as having the same
character set, regardless of the data types of the columns into which
field values are loaded. For proper interpretation of file contents,
you must ensure that it was written with the correct character set. For
example, if you write a data file with mysqldump -T or by issuing a
SELECT ... INTO OUTFILE statement in mysql, be sure to use a
--default-character-set option so that output is written in the
character set to be used when the file is loaded with LOAD DATA INFILE.
*Note*:
It is not possible to load data files that use the ucs2, utf16,
utf16le, or utf32 character set.
If you use LOW_PRIORITY, execution of the LOAD DATA statement is
delayed until no other clients are reading from the table. This affects
only storage engines that use only table-level locking (such as MyISAM,
MEMORY, and MERGE).
If you specify CONCURRENT with a MyISAM table that satisfies the
condition for concurrent inserts (that is, it contains no free blocks
in the middle), other threads can retrieve data from the table while
LOAD DATA is executing. This option affects the performance of LOAD
DATA a bit, even if no other thread is using the table at the same
time.
With row-based replication, CONCURRENT is replicated regardless of
MySQL version. With statement-based replication CONCURRENT is not
replicated prior to MySQL 5.5.1 (see Bug #34628). For more information,
see
http://dev.mysql.com/doc/refman/5.7/en/replication-features-load-data.h
tml.
The LOCAL keyword affects expected location of the file and error
handling, as described later. LOCAL works only if your server and your
client both have been configured to permit it. For example, if mysqld
was started with the local_infile system variable disabled, LOCAL does
not work. See
http://dev.mysql.com/doc/refman/5.7/en/load-data-local.html.
The LOCAL keyword affects where the file is expected to be found:
o If LOCAL is specified, the file is read by the client program on the
client host and sent to the server. The file can be given as a full
path name to specify its exact location. If given as a relative path
name, the name is interpreted relative to the directory in which the
client program was started.
When using LOCAL with LOAD DATA, a copy of the file is created in the
server's temporary directory. This is not the directory determined by
the value of tmpdir or slave_load_tmpdir, but rather the operating
system's temporary directory, and is not configurable in the MySQL
Server. (Typically the system temporary directory is /tmp on Linux
systems and C:\WINDOWS\TEMP on Windows.) Lack of sufficient space for
the copy in this directory can cause the LOAD DATA LOCAL statement to
fail.
o If LOCAL is not specified, the file must be located on the server
host and is read directly by the server. The server uses the
following rules to locate the file:
o If the file name is an absolute path name, the server uses it as
given.
o If the file name is a relative path name with one or more leading
components, the server searches for the file relative to the
server's data directory.
o If a file name with no leading components is given, the server
looks for the file in the database directory of the default
database.
In the non-LOCAL case, these rules mean that a file named as
./myfile.txt is read from the server's data directory, whereas the file
named as myfile.txt is read from the database directory of the default
database. For example, if db1 is the default database, the following
LOAD DATA statement reads the file data.txt from the database directory
for db1, even though the statement explicitly loads the file into a
table in the db2 database:
LOAD DATA INFILE 'data.txt' INTO TABLE db2.my_table;
Non-LOCAL load operations read text files located on the server. For
security reasons, such operations require that you have the FILE
privilege. See
http://dev.mysql.com/doc/refman/5.7/en/privileges-provided.html. Also,
non-LOCAL load operations are subject to the secure_file_priv system
variable setting. If the variable value is a nonempty directory name,
the file to be loaded must be located in that directory. If the
variable value is empty (which is insecure), the file need only be
readable by the server.
Using LOCAL is a bit slower than letting the server access the files
directly, because the contents of the file must be sent over the
connection by the client to the server. On the other hand, you do not
need the FILE privilege to load local files.
LOCAL also affects error handling:
o With LOAD DATA INFILE, data-interpretation and duplicate-key errors
terminate the operation.
o With LOAD DATA LOCAL INFILE, data-interpretation and duplicate-key
errors become warnings and the operation continues because the server
has no way to stop transmission of the file in the middle of the
operation. For duplicate-key errors, this is the same as if IGNORE is
specified. IGNORE is explained further later in this section.
The REPLACE and IGNORE keywords control handling of input rows that
duplicate existing rows on unique key values:
o If you specify REPLACE, input rows replace existing rows. In other
words, rows that have the same value for a primary key or unique
index as an existing row. See [HELP REPLACE].
o If you specify IGNORE, rows that duplicate an existing row on a
unique key value are discarded. For more information, see
http://dev.mysql.com/doc/refman/5.7/en/sql-mode.html#ignore-strict-co
mparison.
o If you do not specify either option, the behavior depends on whether
the LOCAL keyword is specified. Without LOCAL, an error occurs when a
duplicate key value is found, and the rest of the text file is
ignored. With LOCAL, the default behavior is the same as if IGNORE is
specified; this is because the server has no way to stop transmission
of the file in the middle of the operation.
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