MySQL PostgreSQL Oracle Description
ASCII() Return numeric value of left-most character
BIN()       Return a string containing binary representation of a number
BIT_LENGTH()   Return length of argument in bits, vsize of oracle
CHAR_LENGTH() X Return number of characters in argument
CHR(n) x Returns character with ASCII value
CHAR() x x Return character with ascii value
CHARACTER_LENGTH()     length, vsize Synonym for CHAR_LENGTH()
CONCAT_WS()       Return concatenate with separator
CONCAT() Return concatenated string, || SYTANX works with oracle and PostgreSQL only
ELT()       Return string at index number
EXPORT_SET()       Return a string such that for every bit set in the value bits, you get an on string and for every unset bit, you get an off string
FIELD()       Return the index (position) of the first argument in the subsequent arguments
FIND_IN_SET()       Return the index position of the first argument within the second argument
FORMAT()       Return a number formatted to specified number of decimal places
HEX()       Return a hexadecimal representation of a decimal or string value
INSERT()       Insert a substring at the specified position up to the specified number of characters
INSTR() yes no yes Returns the first occurrence index of substring, use position in PostgreSQL db
LCASE()       Synonym for LOWER()
LEFT()       Return the leftmost number of characters as specified
LENGTH()       Return the length of a string in bytes
LIKE       Simple pattern matching
LOAD_FILE()       Load the named file
LOCATE()       Return the position of the first occurrence of substring
LOWER() Returns the all chars in lowercase
LPAD() Return the string with left-padding
LTRIM()   Remove leading spaces
MAKE_SET()       Return a set of comma-separated strings that have the corresponding bit in bits set
MATCH       Perform full-text search
MID()       Return a substring starting from the specified position
NOT LIKE       Negation of simple pattern matching
NOT REGEXP       Negation of REGEXP
OCT()       Return a string containing octal representation of a number
OCTET_LENGTH()       Synonym for LENGTH()
ORD()       Return character code for leftmost character of the argument
POSITION()       Synonym for LOCATE()
QUOTE()       Escape the argument for use in an SQL statement
REGEXP       Pattern matching using regular expressions
REPEAT()       Repeat a string the specified number of times
REPLACE()       Replace occurrences of a specified string
REVERSE() Reverse the characters in a string
RIGHT()       Return the specified rightmost number of characters
RLIKE       Synonym for REGEXP
RPAD() Append chars to the right of the string
RTRIM() Remove trailing spaces
SOUNDEX()       Return a soundex string
SOUNDS LIKE       Compare sounds
SPACE()       Return a string of the specified number of spaces
STRCMP()       Compare two strings
SUBSTR()       Return the substring as specified
SUBSTRING_INDEX()       Return a substring from a string before the specified number of occurrences of the delimiter
SUBSTRING() Return the substring as specified
TRIM()       Remove leading and trailing spaces
UCASE()       Synonym for UPPER(), default print is UPPER
UNHEX()       Return a string containing hex representation of a number
UPPER() Convert to uppercase