If you’re getting an error that reads something like “ERROR 1054 (42S22): Unknown column ‘tab.ColName’ in ‘on clause”” in MariaDB, here are three likely causes:
In SQL Server, we can use the ISNUMERIC() function to return numeric values from a column.
We can alternatively run a separate query to return all values that contain numeric data.
Continue readingWhen using PostgreSQL’s EXCEPT operator, if you encounter an error that reads “ERROR: each EXCEPT query must have the same number of columns“, it’s because there’s a mismatch in the number of columns returned by the queries on either side of the EXCEPT operator.
The way to fix this is to ensure that both SELECT statements return the same number of columns.
In SQLite, we can use the DATE() function to subtract one or more years from a date.
For datetime values, we can use the DATETIME() function.
If you’re getting an error that reads “ERROR 1250 (42000): Table ‘…’ from one of the SELECTs cannot be used in global ORDER clause” when using the UNION clause in a MySQL query, it’s probably because you’re qualifying a column name with its table name.
This doesn’t work in MySQL.
To fix this issue, either remove the table name or use a column alias.
Continue readingThe + operator allows us to add one or more days to a given date in PostgreSQL. We have a few options when it comes to specifying the actual number of days.
Here are eleven options for returning duplicate rows in Oracle Database when those rows have a primary key or some other unique identifier column and you want to ignore it.
Continue readingHere are examples of returning rows that contain non-alphanumeric characters in SQL Server.
Non-alphanumeric characters include punctuation characters like !@#&()–[{}]:;',?/* and symbols like `~$^+=<>“, as well as whitespace characters like the space or tab characters.
SQLite doesn’t have a DATEADD() function like SQL Server (or an ADDDATE() or ADD_DATE() function like in some other DBMSs), but it does have the DATE() function that can make additions to a date value.
SQLite also has a DATETIME() function that can make additions to a datetime value (as well as a TIME() function for time values).
Below are four ways to list out the tables in a MySQL database using SQL or the command line.
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