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.
In PostgreSQL, we can use the chr() function to return a character based on its code.
The code is provided as an integer argument, and the function returns the character that the code represents. When using UTF8 encoding the argument is treated as a Unicode code point, otherwise it must designate an ASCII character.
PostgreSQL has a unistr() function that evaluates escaped Unicode characters in its argument and returns the result as text.
PostgreSQL has a translate() function which replaces certain characters in a string with certain other characters.
We specify the characters in the string that we want to replace, as well as the characters that we want to replace them with. The function then performs the translation and returns the string with the replaced characters.
In PostgreSQL, we can use the to_ascii() function to convert a string to ASCII from another encoding. This usually involves dropping any accents (diacritic signs) from the original string.
We pass the string as an argument to the function. We also have the option of specifying the encoding (either its name or its number).
We can use PostgreSQL’s repeat() function to repeat a string multiple times. We pass the string to the function, along with an integer that specifies how many times we want it repeated, and it returns the string repeated that many times.
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, the regexp_split_to_array() function splits a string using a POSIX regular expression as the delimiter, and returns the result in a text array.
So we use a POSIX regular expression to specify the delimiter/s, and split the string based on that.
We pass the string as the first argument and the pattern as the second. We can also specify a flag to determine how the function behaves.
In PostgreSQL, the regexp_split_to_table() function splits a string using a POSIX regular expression as the delimiter, and returns the result in a table.
So we use a POSIX regular expression to specify the delimiter/s, and split the string based on that.
We pass the string as the first argument and the pattern as the second. We can also specify a flag to change the behaviour of the function.
When using PostgreSQL, we can use the starts_with() function to check whether or not a string starts with a given substring.
We pass the string as the first argument, and the substring as the second.
It returns true if the string does start with the substring, otherwise it returns false.