Here are two options for returning the number of days in a given month in SQLite. This could be the number of days in the current month, or it could be based on a given date.
DBMS
Database Management Systems
SQL IFNULL() Explained
Some RDBMSs provide an IFNULL() function that can be used when dealing with potentially null values. In particular, MySQL, MariaDB, and SQLite each have an IFNULL() function that replaces any null values with another value.
Other RDBMSs, such as SQL Server, Oracle, and PostgreSQL provide similar functionality via functions of a different name.
How ISNULL() Works in MariaDB
In MariaDB, the ISNULL() function checks whether an expression is null or not. If the expression resolves to null, then ISNULL() returns 1, otherwise it returns 0.
Find All Non-Numeric Values in a Column in SQL
If you ever encounter a character column that should be numeric, there’s always a possibility that it contains non-numeric data that you don’t know about.
For example, someone might have set up a Price column as a varchar column that should have been a numeric column, and now you need to clean up after them. You might start by identifying all non-numeric data so that you can work out what to do with it before converting the column to a numeric type.
In SQL, you can run a query to return non-numeric data from the column. The query you use will largely depend on your DBMS.
Find Values That Don’t Contain Numbers in SQL
If you have a column in a database table that contains character data, but some rows also contain numbers, you can use the following SQL queries to return just those rows that don’t contain numbers within the value.
SQL CASE Statement
In SQL, the CASE statement evaluates a list of conditions and returns one of multiple possible result expressions.
In some ways, the SQL CASE statement is kind of similar to the IF...ELSE statement in that it allows us to check for a given condition and return a different result depending on the outcome.