Database Management Systems
There are several ways to show a list of databases in SQL Server. Probably the easiest way is to use the sp_databases stored procedure.
The sp_databases stored procedure is a kind of SQL Server equivalent to the SHOW DATABASES command that can be used with DBMSs such as MySQL and MariaDB. OK, maybe they aren’t strictly equivalents, but based on their ease of use, they could be viewed as such from a user’s perspective.
In MariaDB, 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 there isn’t already one with the same name.
Continue readingWhen using the TO_CHAR() function to format a number in Oracle Database, you can use the V format element to a return a value multiplied by 10n (and if necessary, round it up), where n is the number of 9s after the V.
In MariaDB, we can query the information_schema.tables table to check the size of a database.
This table returns information about the tables and views in each database on the server. We can group the results and return the aggregate amounts for each database.
Continue readingIn 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.
Continue readingMost 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.
In MySQL, 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.
If the table doesn’t exist, it will be created. If it already exists, it won’t be created.
Continue readingMost major RDBMSs provide ways for us to format numbers using SQL. Some provide only basic formatting capabilities, while others are more advanced.
Below are examples of formatting a number in some of the more popular RDBMSs.
Continue readingHere are five ways to check whether or not a table exists in a MySQL database.
Continue readingIn Postgres, we can use the STRING_AGG() function to transform our query results into a comma separated list.
Instead of each value being output in a separate row (as with any regular query), the values are output to a single row, separated by a comma (or some other delimiter of our choosing).
Continue reading