13.2.7 LOAD DATA Syntax

LOAD DATA supports explicit partition selection using the PARTITION option with a list of one or more comma-separated 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 and examples, see Section 23.5, “Partition Selection”.

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 that employ row-level locking, such as InnoDB. For more information, see Partitioning and Locking.

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 character set.

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 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.

LOAD DATA is considered unsafe for statement-based replication. If you do use LOAD DATA when binlog_format=STATEMENT is set, a temporary file containing the data is created on the replication slave where the changes are applied. If binary log encryption is active on the server, note that this temporary file is not encrypted. When encryption is required, be sure to use row-based or mixed binary logging format instead, which do not create the temporary files. For more information on the interaction between LOAD DATA and replication, see Section 17.4.1.19, “Replication and LOAD DATA”.

If you use the LOW_PRIORITY modifier, 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 the CONCURRENT modifier 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 modifier affects the performance of LOAD DATA a bit, even if no other thread is using the table at the same time.

The LOCAL modifier 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 Section 6.1.6, “Security Issues with LOAD DATA LOCAL”.

The LOCAL modifier affects where the file is expected to be found:

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:

Non-LOCAL load operations read text files located on the server. For security reasons, such operations require that you have the FILE privilege. See Section 6.2.2, “Privileges Provided by MySQL”. 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 file contents 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:

The REPLACE and IGNORE modifiers control handling of input rows that duplicate existing rows on unique key values:

To ignore foreign key constraints during the load operation, execute a SET foreign_key_checks = 0 statement before executing LOAD DATA.

If you use LOAD DATA on an empty MyISAM table, all nonunique indexes are created in a separate batch (as for REPAIR TABLE). Normally, this makes LOAD DATA much faster when you have many indexes. In some extreme cases, you can create the indexes even faster by turning them off with ALTER TABLE ... DISABLE KEYS before loading the file into the table and using ALTER TABLE ... ENABLE KEYS to re-create the indexes after loading the file. See Section 8.2.5.1, “Optimizing INSERT Statements”.

For both the LOAD DATA and SELECT ... INTO OUTFILE statements, the syntax of the FIELDS and LINES clauses is the same. Both clauses are optional, but FIELDS must precede LINES if both are specified.

If you specify a FIELDS clause, each of its subclauses (TERMINATED BY, [OPTIONALLY] ENCLOSED BY, and ESCAPED BY) is also optional, except that you must specify at least one of them. Arguments to these clauses are permitted to contain only ASCII characters.

If you specify no FIELDS or LINES clause, the defaults are the same as if you had written this:

Backslash is the MySQL escape character within strings in SQL statements. Thus, to specify a literal backslash, you must specify two backslashes for the value to be interpreted as a single backslash. The escape sequences '\t' and '\n' specify tab and newline characters, respectively.

In other words, the defaults cause LOAD DATA to act as follows when reading input:

Conversely, the defaults cause SELECT ... INTO OUTFILE to act as follows when writing output:

If all the input lines have a common prefix that you want to ignore, you can use LINES STARTING BY 'prefix_string' to skip the prefix and anything before it. If a line does not include the prefix, the entire line is skipped. Suppose that you issue the following statement:

If the data file looks like this:

xxx"abc",1
something xxx"def",2
"ghi",3

The resulting rows will be ("abc",1) and ("def",2). The third row in the file is skipped because it does not contain the prefix.

The IGNORE number LINES option can be used to ignore lines at the start of the file. For example, you can use IGNORE 1 LINES to skip an initial header line containing column names:

When you use SELECT ... INTO OUTFILE in tandem with LOAD DATA to write data from a database into a file and then read the file back into the database later, the field- and line-handling options for both statements must match. Otherwise, LOAD DATA will not interpret the contents of the file properly. Suppose that you use SELECT ... INTO OUTFILE to write a file with fields delimited by commas:

To read the comma-delimited file, the correct statement would be:

If instead you tried to read the file with the statement shown following, it wouldn't work because it instructs LOAD DATA to look for tabs between fields:

The likely result is that each input line would be interpreted as a single field.

LOAD DATA can be used to read files obtained from external sources. For example, many programs can export data in comma-separated values (CSV) format, such that lines have fields separated by commas and enclosed within double quotation marks, with an initial line of column names. If the lines in such a file are terminated by carriage return/newline pairs, the statement shown here illustrates the field- and line-handling options you would use to load the file:

If the input values are not necessarily enclosed within quotation marks, use OPTIONALLY before the ENCLOSED BY option.

Any of the field- or line-handling options can specify an empty string (''). If not empty, the FIELDS [OPTIONALLY] ENCLOSED BY and FIELDS ESCAPED BY values must be a single character. The FIELDS TERMINATED BY, LINES STARTING BY, and LINES TERMINATED BY values can be more than one character. For example, to write lines that are terminated by carriage return/linefeed pairs, or to read a file containing such lines, specify a LINES TERMINATED BY '\r\n' clause.

To read a file containing jokes that are separated by lines consisting of %%, you can do this

FIELDS [OPTIONALLY] ENCLOSED BY controls quoting of fields. For output (SELECT ... INTO OUTFILE), if you omit the word OPTIONALLY, all fields are enclosed by the ENCLOSED BY character. An example of such output (using a comma as the field delimiter) is shown here:

"1","a string","100.20"
"2","a string containing a , comma","102.20"
"3","a string containing a \" quote","102.20"
"4","a string containing a \", quote and comma","102.20"

If you specify OPTIONALLY, the ENCLOSED BY character is used only to enclose values from columns that have a string data type (such as CHAR, BINARY, TEXT, or ENUM):

1,"a string",100.20
2,"a string containing a , comma",102.20
3,"a string containing a \" quote",102.20
4,"a string containing a \", quote and comma",102.20

Occurrences of the ENCLOSED BY character within a field value are escaped by prefixing them with the ESCAPED BY character. Also, if you specify an empty ESCAPED BY value, it is possible to inadvertently generate output that cannot be read properly by LOAD DATA. For example, the preceding output just shown would appear as follows if the escape character is empty. Observe that the second field in the fourth line contains a comma following the quote, which (erroneously) appears to terminate the field:

1,"a string",100.20
2,"a string containing a , comma",102.20
3,"a string containing a " quote",102.20
4,"a string containing a ", quote and comma",102.20

For input, the ENCLOSED BY character, if present, is stripped from the ends of field values. (This is true regardless of whether OPTIONALLY is specified; OPTIONALLY has no effect on input interpretation.) Occurrences of the ENCLOSED BY character preceded by the ESCAPED BY character are interpreted as part of the current field value.

If the field begins with the ENCLOSED BY character, instances of that character are recognized as terminating a field value only if followed by the field or line TERMINATED BY sequence. To avoid ambiguity, occurrences of the ENCLOSED BY character within a field value can be doubled and are interpreted as a single instance of the character. For example, if ENCLOSED BY '"' is specified, quotation marks are handled as shown here:

"The ""BIG"" boss"  -> The "BIG" boss
The "BIG" boss      -> The "BIG" boss
The ""BIG"" boss    -> The ""BIG"" boss

FIELDS ESCAPED BY controls how to read or write special characters:

In certain cases, field- and line-handling options interact:

Handling of NULL values varies according to the FIELDS and LINES options in use:

An attempt to load NULL into a NOT NULL column causes assignment of the implicit default value for the column's data type and a warning, or an error in strict SQL mode. Implicit default values are discussed in Section 11.7, “Data Type Default Values”.

Some cases are not supported by LOAD DATA:

The following example loads all columns of the persondata table:

By default, when no column list is provided at the end of the LOAD DATA statement, input lines are expected to contain a field for each table column. If you want to load only some of a table's columns, specify a column list:

You must also specify a column list if the order of the fields in the input file differs from the order of the columns in the table. Otherwise, MySQL cannot tell how to match input fields with table columns.

Each col_name_or_user_var value is either a column name or a user variable. With user variables, the SET clause enables you to perform preprocessing transformations on their values before assigning the result to columns.

User variables in the SET clause can be used in several ways. The following example uses the first input column directly for the value of t1.column1, and assigns the second input column to a user variable that is subjected to a division operation before being used for the value of t1.column2:

The SET clause can be used to supply values not derived from the input file. The following statement sets column3 to the current date and time:

You can also discard an input value by assigning it to a user variable and not assigning the variable to a table column:

Use of the column/variable list and SET clause is subject to the following restrictions:

When processing an input line, LOAD DATA splits it into fields and uses the values according to the column/variable list and the SET clause, if they are present. Then the resulting row is inserted into the table. If there are BEFORE INSERT or AFTER INSERT triggers for the table, they are activated before or after inserting the row, respectively.

If an input line has too many fields, the extra fields are ignored and the number of warnings is incremented.

If an input line has too few fields, the table columns for which input fields are missing are set to their default values. Default value assignment is described in Section 11.7, “Data Type Default Values”.

An empty field value is interpreted different from a missing field:

These are the same values that result if you assign an empty string explicitly to a string, numeric, or date or time type explicitly in an INSERT or UPDATE statement.

Treatment of empty or incorrect field values differs from that just described if the SQL mode is set to a restrictive value. For example, if sql_mode is set to TRADITIONAL, conversion of an empty value or a value such as 'x' for a numeric column results in an error, not conversion to 0. (With LOCAL or IGNORE, warnings occur rather than errors, even with a restrictive sql_mode value, and the row is inserted using the same closest-value behavior used for nonrestrictive SQL modes. This occurs because the server has no way to stop transmission of the file in the middle of the operation.)

TIMESTAMP columns are set to the current date and time only if there is a NULL value for the column (that is, \N) and the column is not declared to permit NULL values, or if the TIMESTAMP column's default value is the current timestamp and it is omitted from the field list when a field list is specified.

LOAD DATA regards all input as strings, so you cannot use numeric values for ENUM or SET columns the way you can with INSERT statements. All ENUM and SET values must be specified as strings.

BIT values cannot be loaded directly using binary notation (for example, b'011010'). To work around this, use the SET clause to strip off the leading b' and trailing ' and perform a base-2 to base-10 conversion so that MySQL loads the values into the BIT column properly:

shell> cat /tmp/bit_test.txt
b'10'
b'1111111'
shell> mysql test
mysql> LOAD DATA INFILE '/tmp/bit_test.txt'
       INTO TABLE bit_test (@var1)
       SET b = CAST(CONV(MID(@var1, 3, LENGTH(@var1)-3), 2, 10) AS UNSIGNED);
Query OK, 2 rows affected (0.00 sec)
Records: 2  Deleted: 0  Skipped: 0  Warnings: 0

mysql> SELECT BIN(b+0) FROM bit_test;
+----------+
| BIN(b+0) |
+----------+
| 10       |
| 1111111  |
+----------+
2 rows in set (0.00 sec)

For BIT values in 0b binary notation (for example, 0b011010), use this SET clause instead to strip off the leading 0b:

When the LOAD DATA statement finishes, it returns an information string in the following format:

Records: 1  Deleted: 0  Skipped: 0  Warnings: 0

Warnings occur under the same circumstances as when values are inserted using the INSERT statement (see Section 13.2.6, “INSERT Syntax”), except that LOAD DATA also generates warnings when there are too few or too many fields in the input row.

You can use SHOW WARNINGS to get a list of the first max_error_count warnings as information about what went wrong. See Section 13.7.6.40, “SHOW WARNINGS Syntax”.

If you are using the C API, you can get information about the statement by calling the mysql_info() function. See Section 28.7.7.36, “mysql_info()”.

On Unix, if you need LOAD DATA to read from a pipe, you can use the following technique (the example loads a listing of the / directory into the table db1.t1):

mkfifo /mysql/data/db1/ls.dat
chmod 666 /mysql/data/db1/ls.dat
find / -ls > /mysql/data/db1/ls.dat &
mysql -e "LOAD DATA INFILE 'ls.dat' INTO TABLE t1" db1

Here you must run the command that generates the data to be loaded and the mysql commands either on separate terminals, or run the data generation process in the background (as shown in the preceding example). If you do not do this, the pipe will block until data is read by the mysql process.