The SQL SELECT statement is possibly the most commonly used SQL statement. It’s often used to return data from a database, but it can also be used to call functions that return data. The SELECT statement can also be used to return static values, such as string literals.
But the SELECT statement isn’t the only way we can return data in SQL. Another way to return values is with the VALUES statement.
In PostgreSQL the right() function returns the specified number of rightmost characters in a given string.
We have the option of specifying the number of characters to return from the right or the number of characters to omit from the left. We do this by specifying a positive integer (to return n number of rightmost characters) or a negative integer (to return everything except n leftmost characters).
Continue readingIn PostgreSQL we can use the left() function to get the specified number of leftmost characters in a given string.
We have the option of specifying the number of characters to return from the left or the number of characters to omit from the right. We do this by specifying a positive integer (to return n number of leftmost characters) or a negative integer (to return everything except n rightmost characters).
Continue readingThe WHILE loop in SQL Server is a control-flow statement that allows us to repeatedly execute a block of code as long as a specified condition is true. It’s useful for iterative tasks and processing data in batches.
In PostgreSQL, erfc() is a mathematical function that provides the mathematical complementary error function, without loss of precision for large inputs. It returns 1 - erf(x).
The erfc() function was introduced in PostgreSQL 16, which was released on September 14th 2023.
When we create an IDENTITY column in PostgreSQL, we have the option of specifying our own values for the sequence object that’s created.
This article provides an example of creating an IDENTITY column with our own sequence options.
In PostgreSQL, erf() is a mathematical function that provides the standard mathematical error function.
The erf() function was introduced in PostgreSQL 16, which was released on September 14th 2023.
If you’re updating arrays in PostgreSQL and you’ve suddenly realised that some of the arrays aren’t being updated, it could be due to the following.
If you’ve been using the array_append() function and the array_prepend() function, you may have found that one function works but the other doesn’t. For example array_append() works but array_prepend() doesn’t, or vice-versa.
In PostgreSQL, we can use the regexp_replace() function to replace a substring within a given string, based on a given POSIX regular expression. We can specify that all matches are replaced or just the first match.
We pass the string as the first argument, the pattern as the second, and the replacement text as the third argument. We also have the option of specifying the start position as the fourth argument, and we can specify a flag to determine how the function behaves.
Continue readingIn MySQL, the event_scheduler system variable is used to start and stop the Event Scheduler, as well as enable or disable it.
At runtime we can set the value to ON or OFF, and we can check the current value of the variable. We can also disable the Event Scheduler at server startup, but we can’t do this at runtime. However, we can still check the event_scheduler variable to see whether it’s enabled or disabled.