Oracle – Page 4

2 Ways to Convert to Lowercase in Oracle

May 18, 2022 by Ian

Below are two Oracle Database functions that convert uppercase characters to their lowercase equivalent.

Return the Unix Timestamp in SQL

May 16, 2022 by Ian

Below are examples of using some of the more popular RDBMSs to return the Unix timestamp.

The Unix timestamp (also known as Unix Epoch time, Unix time, or POSIX time) is the number of seconds that have elapsed since 00:00:00 Thursday, 1 January 1970, Coordinated Universal Time (UTC).

SQL IFNULL() Explained

May 14, 2022 by Ian

Some RDBMSs provide an IFNULL() function that can be used when dealing with potentially null values. In particular, MySQL, MariaDB, and SQLite each have an IFNULL() function that replaces any null values with another value.

Other RDBMSs, such as SQL Server, Oracle, and PostgreSQL provide similar functionality via functions of a different name.

Find All Non-Numeric Values in a Column in SQL

May 12, 2022 by Ian

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

For example, someone might have set up a Price column as a varchar column that should have been a numeric column, and now you need to clean up after them. You might start by identifying all non-numeric data so that you can work out what to do with it before converting the column to a numeric type.

In SQL, you can run a query to return non-numeric data from the column. The query you use will largely depend on your DBMS.

Find Values That Don’t Contain Numbers in SQL

May 11, 2022 by Ian

If you have a column in a database table that contains character data, but some rows also contain numbers, you can use the following SQL queries to return just those rows that don’t contain numbers within the value.

SQL CASE Statement

May 10, 2022 by Ian

In SQL, the CASE statement evaluates a list of conditions and returns one of multiple possible result expressions.

In some ways, the SQL CASE statement is kind of similar to the IF...ELSE statement in that it allows us to check for a given condition and return a different result depending on the outcome.

SQL NULLIF() Explained

May 8, 2022 by Ian

Most major RDBMSs support the NULLIF() operator, which returns NULL if both of its arguments are equivalent. If the arguments not equivalent, NULLIF() returns the first argument.

NULLIF() is a SQL-standard feature (it’s included in the ISO/IEC 9075 specification).

SQL COALESCE() Explained

May 8, 2022 by Ian

Most major RDBMSs support the COALESCE() operator, which returns the first non-null value from its list of arguments.

COALESCE() is a SQL-standard feature (it’s included in the ISO/IEC 9075 specification).

6 Ways to Delete Duplicate Rows that have a Primary Key in Oracle

May 7, 2022 by Ian

Here are some options for deleting duplicate rows from a table in Oracle Database when those rows have a primary key or unique identifier column.

In such cases, the primary key must be ignored when comparing duplicate rows (due to the fact that primary keys hold unique values).

Detect Whether a Value Contains at Least One Numerical Digit in SQL

May 6, 2022 by Ian

Sometimes you might need to search a database table for only those rows that contain at least one number in a given column.

Technically, numbers can be represented by words and other symbols, but here “number” means “numerical digit”.

Below are examples of how to find rows that contain at least one number in various SQL based DBMSs.