Some RDBMSs like MySQL and MariaDB have a GROUP_CONCAT() function that allows you to return a query column as a delimited list (for example, a comma separated list).
PostgreSQL has a similar function called STRING_AGG(). This function works in pretty much the same way that GROUP_CONCAT() works in MySQL and MariaDB.
In SQL, LPAD()is a commonly used function that pads the left part of a string with a specified character. The function can be used on strings and numbers, although depending on the DBMS, numbers may have to be passed as a string before they can be padded.
DBMSs that have an LPAD() function include MySQL, MariaDB, PostgreSQL, and Oracle.
DBMSs that don’t have an LPAD() function include SQL Server and SQLite (although there are other ways to apply left padding in these DBMSs).
In SQL, RPAD()is used to pad the right part of a string with a specified character. The function can be used on strings and numbers, although depending on the DBMS, numbers may have to be passed as a string before they can be padded.
DBMSs that have an RPAD() function include MySQL, MariaDB, PostgreSQL, and Oracle.
DBMSs that don’t have an RPAD() function include SQL Server and SQLite.
Some DBMSs have functions that allow us to format numbers as currency just by passing the appropriate format string. This converts the number to a string with the applicable currency symbol, group separator, and decimal point (if relevant).
Other DBMSs don’t make it that easy, and you need to do a bit of work first.
Below are examples of using SQL to format numbers as currency in some of the most popular DBMSs.
When using psql to run queries against PostgreSQL, we can use the \pset border and \pset linestyle commands to change the border of the table that displays our results.
Below are five ways to check if a table exists in a PostgreSQL database.
In PostgreSQL, you can use the IF NOT EXISTS clause of the CREATE TABLE statement to check whether or not a table of the same name already exists in the database before creating it.
The table will only be created if no other table exists with the same name. If a table already exists with that name, a “notice” will be issued instead of an error.
Most of the major DBMSs provide us with a way to find a string within a string using SQL. By this, I mean use a SQL query to find the position of a substring within a string.
There are several SQL functions that allow us to do this, including INSTR(), LOCATE(), POSITION(), and CHARINDEX(). The function you use will depend on your DBMS, and possibly whether or not you need to specify a starting position.