Comparison operators are an important part of most programming languages.
Comparison operators are used to compare two expressions. The result is either true or false. It could also be unknown. This could also be represented by either 1, 0, or NULL, depending on the language. These are typically known as “Boolean expressions”.
When used with databases, comparison operators can be used inside your SQL queries to filter data to a certain criteria.
In PostgreSQL, you can use the OVERLAPS operator to test for overlapping time periods.
The function returns true when two time periods (defined by their endpoints) overlap, and false when they do not overlap.
SQLite doesn’t have a concat() function like many other database management systems, such as SQL Server’s concat() and MySQL’s concat().
However, that doesn’t mean you can’t concatenate two strings in SQLite.
SQLite has a concatenation operator (||) that you can use to concatenate two strings.
In SQLite, you can use the LIKE operator in your queries to do a pattern matching comparison.
For example, you can add it to your WHERE clause in order to return only rows that match a given pattern.
However, adding it to the WHERE clause isn’t the only way you can use the LIKE operator. You can also use it to return a boolean value.
MySQL has a number of functions and operators that allow us to perform operations using regular expressions (regex). This article presents two operators and one function that enable us to find out if a string matches a regular expression specified by a given pattern.
These regex functions and operators are:
These are all basically equivalent, as the operators (the second two) are both synonyms of the function (the first one). In any case, you can see examples of all three in action below.
In MySQL, the MATCH() function performs a full-text search. It accepts a comma separated list of table columns to be searched.
The table/s must have a FULLTEXT index before you can do a full-text search against them (although boolean queries against a MyISAM search index can work — albeit slowly — even without a FULLTEXT index).
You can create a FULLTEXT index when creating the table (using the CREATE TABLE statement), or you can use the ALTER TABLE statement or the CREATE INDEX statement if the table already exists.
By default, the search is case-insensitive. To perform a case-sensitive search, use a case-sensitive or binary collation for the indexed columns.