Here are four methods you can use to find duplicate rows in SQL Server.
By “duplicate rows” I mean two or more rows that share exactly the same values across all columns.
Continue readingCategory: DBMS
Database Management Systems
3 Ways to List All Stored Procedures that Reference a Table in PostgreSQL
Here are three examples of returning a list of stored procedures that reference a specific table in PostgreSQL.
Continue reading3 Ways to List all Triggers for a Given Table in PostgreSQL
Here are three options for listing out the triggers for a given table in PostgreSQL.
Continue readingMariaDB UNION Operator Explained
In MariaDB, the UNION operator combines the results from multiple SELECT statements into a single result set.
Return Rows that Only Contain Non-Alphanumeric Characters in SQLite
Here’s an example of returning rows that contain only non-alphanumeric characters in SQLite.
Non-alphanumeric characters include punctuation characters like !@#&()–[{}]:;',?/* and symbols like `~$^+=<>“, as well as whitespace characters like the space or tab characters.
MariaDB INTERSECT Operator Explained
In MariaDB, the INTERSECT operator intersects two queries and returns only those rows that are returned in both queries.
It returns all rows from the left SELECT result set that are also present in the right SELECT result set.
6 Ways to Select Duplicate Rows in SQLite
The following queries can be used to return duplicate rows in SQLite.
Here, the duplicate rows contain duplicate values across all columns, including the ID column.
Continue readingMariaDB EXCEPT Operator Explained
In MariaDB, the EXCEPT operator returns rows from the left input query that aren’t output by the right input query.
Another way of putting it is that it returns all rows from the left SELECT result set except rows that are in right SELECT result set.
5 Ways to Select Rows with the Maximum Value for their Group in SQL
Here are five options for using SQL to return only those rows that have the maximum value within their group.
These examples work in most major RDBMSs, including MySQL, MariaDB, Oracle, PostgreSQL, SQLite, and SQL Server.
Continue reading3 Ways to Create a Table if it Doesn’t Already Exist in Oracle
The very useful CREATE TABLE IF NOT EXISTS syntax was finally introduced in Oracle Database – Oracle Database 23c to be precise. This syntax allows us to run a CREATE TABLE statement without getting an error if the table already exists.
Earlier versions of Oracle don’t support the IF NOT EXISTS clause, and so if we want to avoid any nasty errors resulting from trying to create a table that already exists, we need to do a bit of extra work.