In SQLite, we can use the TIME() function to subtract one or more minutes from a time value.
For datetime values, we can use the DATETIME() function.
Category: SQLite
Return Rows that Contain Only Alphanumeric Characters in SQL
Alphanumeric characters are alphabetic characters and numeric characters.
Below are examples of using SQL to return rows that contain only alphanumeric characters.
Continue readingSQL ISNULL() Explained
Some RDBMSs provide an ISNULL() function that can be used when dealing with potentially null values.
MySQL, MariaDB, and Oracle Database each have an ISNULL() function that returns 1 if its argument is null, and 0 if it’s not.
SQL Server also has an ISNULL() function, but it works differently. It works more like how the IFNULL() function works in some other RDBMSs.
Other RDBMSs, such as PostgreSQL and SQLite don’t include an ISNULL() function, but they do support the IS NULL predicate (as do the other RDBMSs).
Add Seconds to a Time Value in SQLite
In SQLite, we can use the TIME() function to add a given number of seconds to a time value.
If we’re dealing with datetime values, we can use the DATETIME() function.
Return the Unix Timestamp in SQL
Below are examples of using some of the more popular RDBMSs to return the Unix timestamp.
The Unix timestamp (also known as Unix Epoch time, Unix time, or POSIX time) is the number of seconds that have elapsed since 00:00:00 Thursday, 1 January 1970, Coordinated Universal Time (UTC).
Continue reading2 Ways to Get the Number of Days in a Month in SQLite
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.
Continue readingSQL 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.
Continue readingFind 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.
Continue readingFind 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.
Continue readingSQL 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.