In PostgreSQL, an array constructor is an expression that builds an array value using values for its member elements.
One of the things we can do is build an array based on the results of a subquery.
how to
Fix ‘time zone … not recognized’ in PostgreSQL
If you’re getting an error that reads something like ‘time zone “US/New_York” not recognized‘ in PostgreSQL while using a function such as date_add(), date_subtract() or date_trunc(), it’s probably because you’re specifying an unsupported time zone.
If you specify a time zone, it must be one that’s recognised by the system.
To fix this issue, either provide a recognised time zone or omit the time zone argument altogether (assuming this is a valid option for the situation).
2 Functions that Return a Substring in PostgreSQL
PostgreSQL has an extensive collection of built-in string functions that allow us to manipulate text values. One task we might want to perform is to extract a substring from a larger string. Fortunately, PostgreSQL caters for our needs with at least two functions that make this a breeze.
Fix “function array_shuffle(numeric) does not exist” in PostgreSQL
If you’re getting an error that reads “function array_shuffle(numeric) does not exist” when using the array_shuffle() function in PostgreSQL, it’s probably because the argument you’re passing to the function is not an array.
More specifically, this error message implies that you’re passing a numeric type. The same error can occur when passing other non-array types (such as integer), but the solution is the same.
The argument for this function must be an array.
To fix this error, replace the numeric value with an array value when calling the array_shuffle() function.
Fix Error “cannot determine type of empty array” in PostgreSQL
If you’re getting an error that reads “cannot determine type of empty array” in PostgreSQL, it could be that you’re trying to create an empty array without specifying the array type.
It’s impossible to create an array with no type, and so if we want to create an empty array, then we need to specify the type or add items to determine the type.
To fix this issue, either specify the array type for the empty array, or add items to the array.
4 Ways to Append an Element to an Array in PostgreSQL
We have several options when it comes to appending elements to arrays in PostgreSQL. We can use an operator to concatenate the value to the array or we can use a function to do the job.
Below are four ways to append elements to arrays in PostgreSQL.
Fix Error “time field value out of range” when using make_time() in PostgreSQL
If you’re getting an error that reads ‘time field value out of range‘ in PostgreSQL while using the make_time() function, it’s probably because one or more of the time parts you’re providing is out of the accepted range for that time part.
To fix this issue, be sure that each time part you provide is within the valid range for that time part.
Fix Error “column … cannot be cast automatically to type …” in PostgreSQL
If you’re getting an error that reads something like ‘column “c1” cannot be cast automatically to type text[]‘ in PostgreSQL, it could be that you’re trying to change a column’s type to one where the existing type can’t be implicitly cast to.
To fix this issue, try explicitly casting the column to the desired data type.
Fix “function array_sample(numeric, integer) does not exist” in PostgreSQL
If you’re getting an error that reads “function array_sample(numeric, integer) does not exist” when using the array_sample() function in PostgreSQL, it’s probably because your first argument is a numeric type instead of an array.
The first argument for this function must be an array.
To fix this error, be sure that your first argument to array_sample() is an array, not a numeric value.
How to Create a MySQL Event Only if it Doesn’t Already Exist
In MySQL we can use the CREATE EVENT statement to create scheduled events. As with many CREATE ... statements, we have the option of using the IF NOT EXISTS clause to specify that the object should only be created if it doesn’t already exist.
Of course, we wouldn’t normally be trying to create an event if we know that it already exists. But there may be times where we’re not sure, and we want our code to handle this scenario without throwing an error if an event with the same name already exists. This is common when creating scripts that are designed to be run across multiple environments. That’s where the IF NOT EXISTS clause can come in handy.