In PostgreSQL, the md5() function computes the MD5 hash of the specific text, and outputs the result in hexadecimal.
We pass the text as an argument when calling the function.
Object-Relational
How to DROP Tables with Foreign Key Relationships in PostgreSQL
Nothing pulls me out of the “zone” quicker than attempting to drop a table, only to be told “Nope, that table has a dependency!”.
Granted, this usually only happens in my development environments, as I rarely have any need to drop tables in a production environment.
And that’s probably why it “pulls me out of the zone”. I suddenly have to stop and start thinking about what tables contain foreign keys to the one I’m trying to drop. In dev environments, we’re often trying things out and so it’s not out of the question that we might inadvertently try to drop a table without realising it has dependent objects.
Fortunately, when we’re working with PostgreSQL, we have a quick and easy method to overcome this barrier.
2 Functions that Return the Position of a Substring within a String in PostgreSQL
PostgreSQL sometimes provides us with multiple functions that basically do the same thing. Such is the case with the following two functions that return the position of a given substring within a string.
A Quick Look at TO_HEX() in PostgreSQL
In PostgreSQL, we can use the to_hex() function to convert a number to its equivalent hexadecimal representation.
The function accepts the number as an integer or bigint, and it returns the result as a text representation of its hexadecimal equivalent.
How to Specify your own Subscript Range when Creating an Array in PostgreSQL
By default, PostgreSQL arrays are one-based. This means that we need to use 1 if we want to reference the first element in the array, 2 for the second, and so on.
But we also have the option of specifying our own subscript range for an an array. For example we could create a zero-based array, a ten-based array, or even a negative value such as a negative ten-based array.
We can do this by using subscripted assignment to specify the actual subscript range for the array. Basically, we prefix the array with the subscript range, enclosed in square brackets, and an equals sign (=) between it and the array.
A Quick Look at the ASCII() Function in PostgreSQL
In PostgreSQL, we can use the ascii() function to get the numeric code of the first character of the argument.
When using UTF8, the function returns the Unicode code point of the character. Other multibyte encodings require an ASCII character.
Understanding PostgreSQL’s SPLIT_PART() Function
The PostgreSQL split_part() function splits a string based on a specified delimiter and then returns the specified part from the split string.
The function accepts three arguments; the string, the delimiter, and the part that we want to return.
A Quick Look at PostgreSQL’s PG_CLIENT_ENCODING() Function
In PostgreSQL, we can use the pg_client_encoding() function to get the current client encoding name.
Understanding the RIGHT() Function in PostgreSQL
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).
A Quick Look at the LEFT() Function in PostgreSQL
In 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).