string-comparison

I've been trying to figure out how I can make a query with MySQL that checks if the value (string $haystack ) in a certain column contains certain data (string $needle ), like this: mysql_query(" SELECT * FROM `table` WHERE `column`.contains('{$needle}') "); In PHP, the function is called substr($haystack, $needle) , so maybe: WHERE substr(`column`, '{$needle}')=1 Quite simple actually: mysql_query(" SELECT * FROM `table` WHERE `column` LIKE '%{$needle}%' "); The % is a wildcard for any character. Do note that this can get slow on very large datasets so if your database grows you'll need to

When should one compare String s as objects and when should one use their equals method? To make sure, I always use equals , but that doesn't seem very efficient. In what situations can I be certain that string1 == string2 is a safe to use? Thanks! You should almost always use equals . You can be certain that string1 == string2 will work if: You've already made sure you've got distinct values in some other way (e.g. you're using string values fetched from a set, but comparing them for some other reason) You know you're dealing with compile-time string constants You've manually interned the

What does "compare two strings lexicographically" mean? Leading from answers from @Bozho and @aioobe, lexicographic comparisons are similar to the ordering that one might find in a dictionary. The Java String class provides the .compareTo () method in order to lexicographically compare Strings. It is used like this "apple".compareTo ("banana") . The return of this method is an int which can be interpreted as follows: returns < 0 then the String calling the method is lexicographically first (comes first in a dictionary) returns == 0 then the two strings are lexicographically equivalent returns

I would like to know how to check whether a string starts with "hello" in Python. In Bash I usually do: if [[ "$string" =~ ^hello ]]; then do something here fi How do I achieve the same in Python? RanRag aString = "hello world" aString.startswith("hello") More info about startwith Shawabawa RanRag has already answered it for your specific question. However, more generally, what you are doing with if [[ "$string" =~ ^hello ]] is a regex match. To do the same in Python, you would do: import re if re.match(r'^hello', somestring): # do stuff Obviously, in this case, somestring.startswith('hello')