The following examples use T-SQL to delete duplicate rows in SQL Server while ignoring the primary key or unique identifier column.
More specifically, the examples delete duplicate rows but keep one. So, given two identical rows, one is deleted and the other remains. This is often referred to as “de-duping” the table, “deduplication” of the table, etc.
When using the UNION operator in MariaDB, you may encounter the following error: “ERROR 1222 (21000): The used SELECT statements have a different number of columns”.
This error occurs when the number of columns returned by each SELECT statement is different.
The way to fix this is to ensure that both SELECT statements return the same number of columns.
In PostgreSQL, we can use the + operator to add one or more years to a date.
The following MySQL query returns only those rows that have numeric values in a given column.
The following options can be used to delete duplicate rows in Oracle Database.
These examples delete duplicate rows but keep one. So if there are three identical rows for example, it deletes two of them and keeps one. This is often referred to as de-duping the table.
If you’re getting an error that reads something like “ERROR 1136 (21S01): Column count doesn’t match value count at row 2” when using the VALUES statement in MySQL, it’s probably because there’s a mismatch in the number of columns specified in the ROW() clauses.
To fix this error, be sure that all ROW() clauses contain exactly the same number of columns.
We can use SQLite’s DATE() function to return the date of the first instance of a given day of a given year. Therefore, we can use it to return the first Monday of a given year. We can also use it to return the first Tuesday, Wednesday, Thursday, Friday, etc.
We can use DATETIME() if we want a datetime value to be returned.
Below are five options for returning rows that contain uppercase letters in SQL Server.
If you’re using one of SQLite’s tabular output modes, you might find yourself battling with long lines of text that result in all subsequent columns being pushed out far to the right. This can cause you to have to keep scrolling sideways as you peruse the data.
Fortunately, there’s an easy fix.
MySQL and MariaDB have a SHOW TABLES statement, which outputs a list of tables and views in a database. PostgreSQL doesn’t have a SHOW TABLES statement, but it does have a command that produces a similar result.
In Postgres, you can use the \dt command to show a list of tables. This is a psql command (psql is the interactive terminal for PostgreSQL).