Database Management Systems
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.
Below are two functions that convert lowercase characters to their uppercase equivalent in Oracle Database.
Both functions work in a similar way, but with a minor difference.
Continue readingThe following SQLite example returns all rows that contain at least one numerical digit.
Continue readingIn SQL Server, the COALESCE() expression returns its first non-null argument.
The way it works is, we pass a list of arguments to the expression, it evaluates the arguments in order and returns the current value of the first expression that initially doesn’t evaluate to NULL.
When using SQLite, we can use the following methods to extract data from a JSON document.
Continue readingIn MariaDB, we can use the LAST_DAY() function to return the last day of a given month.
This could be the last day of the current month, or the last day of the month based on a date that we specify.
Continue readingHere’s an option for returning the Unix timestamp when using Oracle Database.
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 readingThe following example deletes duplicate rows in MySQL while ignoring the primary key or unique identifier column.
The example deletes duplicate rows but keeps one. So in the case of two identical rows, it deletes one of them and keeps the other.
Continue readingIn SQL Server, we can use the following method to return a date and time based on a given 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 readingIn PostgreSQL, we can use the extract() function along with the epoch argument to return the Unix timestamp.
We can return the Unix timestamp based on the current date/time, or we can get it based on another specified date/time.
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