mysql SUBSTRING function keyword split the string for a field into sub strings.

mysql limit keyword optimiztion.. instead of getting all rows in a table you can get a small group of rows that needed to your word!… by this you save server resources.

BIT_LENGTH(str) function Returns the length of the string str in bits.

mysql ASCII function keyword is used to return the numeric value of the leftmost character of the string ’str’. Returns 0 if ’str’ is the empty string and  returns NULL if str is NULL.

CONCAT(str1,str2,…) Returns the string that results from concatenating the arguments to gother. May have one or more arguments.

CHAR_LENGTH(str) function Returns the length of the string str, measured in characters. A multi-byte character counts as a single character.

Sometimes you need to return a limited number of rows such as selecting the first 10 rows of some table, web will show how to do this using MySQL, Sql Server and Oracle

For some reasons you may want to select some random records from a table to perform some processing on them,  I will show how to Select random records in MySQL