In MariaDB, the COALESCE() operator returns the first non-NULL value in the list, or NULL if there are no non-NULL values.
Category: DBMS
Database Management Systems
MySQL NULLIF() Explained
In MySQL, NULLIF() is a flow control function that returns NULL if both of its arguments are equivalent. Otherwise it returns the first argument.
Return Non-Numeric Values from a PostgreSQL Database Column
The following PostgreSQL examples return only those rows that don’t have a numeric value in a given column.
Continue reading7 Ways to Find Duplicate Rows in PostgreSQL while Ignoring the Primary Key
Here are seven ways to return duplicate rows in PostgreSQL when those rows have a primary key or other unique identifier column.
This means that the duplicate rows share exactly the same values across all columns with the exception of their primary key/unique ID column.
Continue readingHow to Get the Number of Days in a Month in MySQL
Check out the following technique in MySQL if you need to find out how many days are in a month based on a given date.
Continue readingConvert a Unix Timestamp to a Date Value in Oracle
In Oracle Database, we can use the following technique to return a date from a Unix timestamp value.
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 readingJSON_INSERT() vs JSON_SET() vs JSON_REPLACE() in SQLite
SQLite provides several functions for inserting, setting, and replacing values in a JSON document. Specifically, it provides json_insert(), json_set(), and json_replace().
These functions perform similar tasks, and you can sometimes use them interchangeably to a certain point.
But there is definitely a clear difference between each function.
Continue readingMySQL COALESCE() Explained
In MySQL, the COALESCE() operator returns the first non-NULL value in the list, or NULL if there are no non-NULL values.
Subtract Months from a Date in PostgreSQL
In PostgreSQL, we can use the - operator to subtract one or more months from a date.
Get the First, Second, Third, or Fourth Monday of a Month in SQLite
We can use SQLite’s DATE() function to perform calculations on a given date. One of the things we can do is return the first, second, third, or fourth instance of a given day within a given month.