In PostgreSQL we can create auto-incrementing columns using the serial data type. The serial type causes the column to be automatically populated with an auto-incrementing value each time a new row is inserted. The same applies for the smallserial and bigserial types.
This article provides an overview of how these data types work.
Continue readingPrior to PostgreSQL 10, if we wanted to create an auto-incrementing column, we would typically use the SERIAL type, or we’d create our own sequence and apply it to an integer column.
But from PostgreSQL 10 onwards, we’ve been able to create identity columns.
Continue readingWhen using relational database management systems (RDBMSs) we often hear terms like DDL, DML, DQL, TCL, and DCL. But what exactly are they?
In this article we’ll look at what DCL stands for in the context of SQL, and what it does.
Continue readingIf you’re getting an error that reads something like “Cannot drop a default constraint by DROP DEFAULT statement. Use ALTER TABLE to drop a constraint default“, it’s because you’re trying to use DROP DEFAULT to drop a DEFAULT constraint.
The DROP DEFAULT statement has been flagged for deletion from SQL Server, and Microsoft recommends that we use the ALTER TABLE statement to drop DEFAULT constraints.
Therefore, to fix this issue, use the ALTER TABLE statement to drop the DEFAULT constraint.
We often hear terms like DDL, DML, DQL, TCL, and DCL when using relational database management systems (RDBMSs). But what exactly are they?
In this article we’ll look at what DQL stands for, and what it does.
Continue readingIf you’re getting an error that reads “ERR wrong number of arguments for ‘hstrlen’ command“, it’s because you’re passing the wrong number of arguments when using the HSTRLEN command.
The HSTRLEN command requires two arguments (at the time of writing). These are the name of the key and the name of the field.
If you’re getting this error, check the number of arguments that you’re passing and adjust if required.
Continue readingWe often hear terms like DDL, DML, DQL, and DCL when using relational database management systems (RDBMSs). But what exactly are they?
In this article we’ll look at what DML stands for, and what it does.
Continue readingIf you’re getting an error in MySQL that reads something like “ERROR 1054 (42S22): Unknown column ‘c.DogName’ in ‘on clause”“, here are three likely causes:
We often encounter terms like DDL, DML, DQL, DCL, and TCL when using relational database management systems (RDBMSs). But what do they mean?
In this article we’ll look at what DDL stands for and what it does.
Continue readingThe following is a list of date and time functions available in MySQL. Click on each function name to see an explanation of the function, its syntax, and examples.
Continue reading