If you’ve worked with SQL Server long enough, you’ve probably run into the dreaded “Only one expression can be specified in the select list when the subquery is not introduced with EXISTS” error. This error usually pops up when you try to use a subquery in a place where SQL Server expects a single value, but your query is returning multiple columns or multiple rows.
It’s a simple mistake, but it can be frustrating until you understand why it happens and how to fix it.
If you’ve worked with SQL Server for a while, you’ve probably run into the dreaded 4101 error that looks something like Msg 4104, Level 16, State 1, Line X: The multi-part identifier “X.Y” could not be bound.
It’s one of those vague errors that doesn’t immediately tell you what’s wrong. Basically SQL Server is complaining because it doesn’t know how to resolve the reference you wrote. This is usually a column or alias.
Let’s take a look at the most common causes, with examples to make them easier to spot.
When you’re working with SQL Server, sometimes you don’t just want to throw an error. Sometimes you want to build a message you can actually use elsewhere. That’s where FORMATMESSAGE() comes in. Instead of immediately printing a message like RAISERROR does, FORMATMESSAGE() gives you the formatted string back so you can decide what to do with it. This could include logging it, storing it, displaying it, or simply passing it along.
In simple terms, you can think of it as a way to take a predefined message from sys.messages (or even a custom string you provide) and turn it into a neatly formatted output. This can be quite handy when you need more control over how messages are handled in your SQL workflows.
Data conversion errors can be a frequent source of frustration when working with databases. And SQL Server is no exception. Such errors can interrupt workflows and lead to inconsistent results. While data conversion errors often happen during explicit conversions, they aren’t unique to this. Oftentimes the error can be due to an implicit conversion.
This article outlines five of the most common data conversion errors and provides practical steps to avoid them.
DuckDB offers two primary functions for type conversion: cast() and try_cast(). While they serve similar purposes, their behavior when handling invalid conversions differs significantly, which can greatly impact our data processing workflows.
If you’re getting an error that reads “AUTOINCREMENT is only allowed on an INTEGER PRIMARY KEY” in SQLite, it appears that you’re trying to define a column as an AUTOINCREMENT on a column that’s not defined as INTEGER PRIMARY KEY.
SQLite only allows us to use AUTOINCREMENT on INTEGER PRIMARY KEY columns.
To address this issue, be sure to make the column an INTEGER PRIMARY KEY if you need to use AUTOINCREMENT on it.
If you’re getting an error in DuckDB that includes “list dimensions must be equal“, it appears that you’re performing a list operation that requires the lists to be the same dimension, but the lists are of different dimensions.
To fix this error, be sure to use lists of equal dimensions when performing the operation.
Encountering errors while converting between data types can be frustrating when working with SQL databases like DuckDB. But it usually means that something’s wrong. In most cases these errors occur because we’re trying to perform an impossible conversion, like from a number to a date or something.
But sometimes errors can get in the way, especially when we’re trying to convert a bunch of values. Sometimes it would be better for the system to return NULL for such failed conversions than to return an error and mess up the whole operation. Fortunately, we can do this.
If you’re getting a binder error that reads something like “No function matches the given name and argument types ‘list_concat(STRING_LITERAL, VARCHAR[][])’. You might need to add explicit type casts.” in DuckDB when using either the array_push_front() or array_push_back() functions, it could be due to a slight syntax error.
If you’re getting an error that reads something like “Macro function generate_subscripts(arr, dim) requires 2 positional arguments” in DuckDB, it appears that you’re calling the generate_subscripts() function with the wrong number of arguments.
