Mysql - Load data infile query for Particular Values
IMHO there is no a perfect solution for such scenario but you can utilize IGNORE clause.

For example if you were to have an auto_increment id column in your table and you already have a row in it with a known id then your query to import only rows for february might look like this

LOAD DATA local INFILE  '/path/to/your/file.txt' IGNORE
INTO TABLE slsdata 
FIELDS TERMINATED BY '\t'   
LINES TERMINATED BY '\n'  
IGNORE 1 LINES
(@sldate)
SET id = IF(MID(@sldate, 6, 2) = '02', NULL, 1), sldate = @sldate


What it does it reads values of sldate field in @slfield variable then in SET clause it checks whether it's february and if it is then assigns NULL to id column and if not then assigned predefined existing value 1 violating a UNIQUE constraint and IGNORE clause does exactly that it skips a row in such a case.



That being said I'd recommend another approach:


create a temporary staging table without any constraints
load whole file in it
do all necessary cleansing, validating against ref tables, transformations etc. on required subset of data (e.g. for particular month) utilizing all SQL capabilities
insert required subset of data from staging table into your factual table
truncate or drop staging table