DBMS – Page 165

Example of a Simple Merge Statement in SQL Server

February 24, 2022 by Ian

The following example uses T-SQL to merge two tables in SQL Server. It uses the VALUES table value constructor as the source table.

PostgreSQL DATEADD() Equivalent

April 20, 2024February 24, 2022 by Ian

Updated 20 April 2024 to include the date_add() function.

SQL Server has its DATEADD() function that adds an interval to a date value. MySQL’s DATE_ADD() and ADDDATE() for does the same thing, as does MariaDB’s DATE_ADD() and ADDDATE(). SQLite has a DATE() function that also provides the option of adding an interval to a given date.

Prior to version 16, PostgreSQL didn’t have a DATEADD() or equivalent function. But with PostgreSQL 16 came with the introduction of the date_add() function, which allows us to add an interval to a timestamp with time zone.

We can also add and subtract values from dates with date/time operators such as + and -.

3 Ways to Convert an Integer to Decimal in SQL Server

February 23, 2022 by Ian

Here are three options for converting an integer to a decimal value in SQL Server using T-SQL.

PostgreSQL VALUES Command Explained

February 24, 2022February 23, 2022 by Ian

In PostgreSQL, the VALUES command returns a set of one or more rows as a table. It’s a table value constructor that can be used as part of a larger command, or as a standalone SQL statement.

SQL Server SHOW TABLES Equivalent

February 22, 2022 by Ian

Every now and then I find myself typing SHOW TABLES in SQL Server, expecting to get a list of tables.

That would make perfect sense if I was using MySQL or MariaDB. But SQL Server/T-SQL doesn’t have a SHOW TABLES statement like MySQL or MariaDB, so it never works. And I keep forgetting. But fortunately, SQL Server does have alternatives.

Here are five options for getting a list of tables in SQL Server. These can be used whenever you’re trying to find that elusive SHOW TABLES statement in SQL Server.

SQLite INTERSECT Operator

February 22, 2022 by Ian

In SQLite, the INTERSECT operator is used to create a compound SELECT statement that returns the intersection of the results of the left and right SELECT statements. In other words, it combines two queries, but returns only those rows that are returned in both queries.

SQLite EXCEPT Operator

February 21, 2022 by Ian

In SQLite, the EXCEPT operator can be used to create a compound SELECT statement that returns the subset of rows returned by the left SELECT that are not returned by the right SELECT.

Fix Msg 512 “Subquery returned more than 1 value” in SQL Server

September 17, 2024February 21, 2022 by Ian

If you get error Msg 512 that reads “Subquery returned more than 1 value…” in SQL Server, it’s because you’re using a subquery that returns more than one value in a scenario where this is not allowed.

Find All Non-Numeric Values in a Column in Oracle

February 20, 2022 by Ian

If you ever encounter a character column that should be a numeric column, there’s always a possibility that it contains non-numeric data that you don’t know about.

In Oracle Database, you can run a query like the following to return non-numeric data from the column.

SQLite UNION Operator

February 20, 2022 by Ian

In SQLite, the UNION operator creates a compound SELECT statement that returns the results of the left and right SELECT statements. In other words, it combines the results from two queries into a single result set.