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.
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.
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.
If you’re getting an error that reads ‘date/time field value out of range‘ in PostgreSQL while using a function such as date_add(), date_subtract(), or date_trunc(), it’s probably because the date value you’re passing to the function is an invalid date.
It’s possible that you’ve got the month and day in the wrong order.
To fix this issue, be sure that you pass a valid date. It may be that all you need to do is switch the day and the month around. Or it could be that you need to change your datestyle setting.
If you’re getting an error that reads “ERROR: cannot take logarithm of zero” when using either the log() function or log10() function in PostgreSQL, it’s probably because you’re passing an argument of zero.
These functions require a value greater than zero. This is true even for the base argument of the log() function (the argument that specifies which base to use).
To fix this issue, be sure to pass a value greater than zero to these functions.
PostgreSQL provides us with a handful of string functions that return the length of a given string.
But the result between these functions can be different, depending on which function we use. That’s because the “length” can be different, depending on what we’re measuring. Are we talking about the number of characters in the string? Or the number of bytes in the string? Or perhaps we want to know the number of bits in the string.
The function we use will depend on which of the above we’re trying to measure. Below are five functions that cater for each of the above questions.
In PostgreSQL, we can use array constructors to create arrays that contain elements that we specify. We can populate the array from literal values, or we can let a query provide the values.
We can also create multi-dimensional arrays. When populating the array from a query, we can use multiple subqueries to create each sub-array. Therefore we can create a multi-dimensional array from a query.
If you’re getting an error that reads “ERROR: cannot take logarithm of a negative number” when using either the log() function or log10() function in PostgreSQL, it’s probably because you’re passing a negative value to the function.
These functions require a value greater than zero. This is true even for the base argument of the log() function (the argument that specifies which base to use).
To fix this issue, be sure to pass a value greater than zero to these functions.
In PostgreSQL, an array constructor is an expression that builds an array value using values for its member elements.Â
One of the things we can do is build an array based on the results of a subquery.
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).