In MySQL, you can unhex a string using the UNHEX() function. But you can’t unhex a number with that function.
To unhex a number in MySQL, use the CONV() function instead.
The CONV() function allows you to convert numeric values between different numbering systems. For example, you can convert between say decimal and binary, octal to decimal, or, more relevant to this article, between hexadecimal and decimal.
One of the string functions in MySQL is STRCMP(). This function allows you to compare two strings according to their sort order.
The function accepts two arguments. Each argument is the string to compare. It returns either 1, -1, or 0, depending on whether the first string is larger, smaller, or the same size as the second string, according to sort order.
One of the many MySQL string functions is the SOUNDEX() function. This function returns a Soundex string from a given string. If two words sound the same, they should have the same Soundex string. If two words sound similar, but not exactly the same, their Soundex string might look similar but not exactly the same.
This article contains a bunch of Soundex examples to demonstrate how the SOUNDEX() function works in MySQL.
If you need to convert a number from decimal to octal (base 8), two functions come to mind if you’re using MySQL. One function is specifically for doing octal conversions, the other is for doing conversions between different bases. These are as follows:
OCT()CONV()More about these two functions below.
Sometimes you need to pad a string with spaces. Or perhaps you’ll pad it with another character. Sometimes you need to pad it on the left. Other times you need to pad it on the right. Or maybe you need to pad it on both sides.
All of the above can be done in MySQL using the LPAD() and/or RPAD() string functions.
When working with MySQL, you might occasionally encounter situations where you need to pad a bunch of numbers with leading zeros.
Perhaps you have a requirement that all numbers have three digits, but in the data you’ve been supplied, the numbers range from a single digit, to two, and maybe three digits. Your requirement might be to pad all numbers with leading zeros, but only to make up for any shortfall in the three digit requirement.
The LPAD() function does exactly what you want in this scenario.
The MySQL REPLACE() function enables you to replace all occurrences of a substring with another string. It allows you to do things like, replace all occurrences of one word with another word, etc.
This article demonstrates its usage.
Using a backslash to escape single quotes is a commonly used technique to ensure that the single quotes don’t interfere with MySQL‘s handling of the full string.
Single quotes are used to surround a string, so a single quote within the string itself could cause havoc if it isn’t properly escaped. Simply inserting a backslash immediately before the quote mark ensures that MySQL doesn’t terminate the string prematurely.
However, there may be occasions where you want the backslash to remain. For example, you might intend to use the string in an SQL statement, and therefore, you want it to be properly escaped first.
This is where the QUOTE() function comes in.
The MySQL QUOTE() function quotes a string to produce a result that can be used as a properly escaped data value in an SQL statement. The string is returned enclosed by single quotation marks and with each instance of backslash (\), single quote ('), ASCII NUL, and Control+Z preceded by a backslash.
MySQL has a number of string functions that return the position of a substring within a string. More specifically, they return the position of the first occurrence within the string (or the first occurrence after a given starting point).
The functions I’m referring to are as follows:
INSTR()LOCATE()POSITION()Below is an overview of each one.