In MySQL, NULLIF() is a flow control function that returns NULL if both of its arguments are equivalent. Otherwise it returns the first argument.
Category: DBMS
Database Management Systems
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.
Fix “At least one of the arguments to COALESCE must be an expression that is not the NULL constant” in SQL Server
In SQL Server, if you’re getting error Msg 4127 that reads “At least one of the arguments to COALESCE must be an expression that is not the NULL constant”, it’s probably because all of your arguments to the COALESCE() expression are the NULL constant.
To fix this issue, make sure at least one argument is not the NULL constant.