Tag: how to

How to Create a Unique Index in SQLite

Posted on by Ian

SQLite is a lightweight, serverless SQL database engine commonly used for developing mobile applications, web applications, and embedded systems. Among its various functionalities, SQLite allows developers to create indexes, including unique indexes, to enhance data retrieval speed and enforce constraints on data integrity.

A unique index ensures that all values in a specific column, or combination of columns, are distinct, preventing duplicate entries.

In this guide, we’ll walk through the basics of unique indexes in SQLite, explore when and why to use them, and provide examples of how to create them.

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Fix “Binder Error” When Using COALESCE() in DuckDB

Posted on by Ian

If you’re getting an error that reads something like “Binder Error: Cannot mix values of type …etc” when using the COALESCE() function in DuckDB, it’s probably because you’re using arguments with incompatible types.

To fix this issue, try using CAST() or TRY_CAST() to ensure that all arguments are compatible. Alternatively, make sure the arguments to COALESCE() are of the same type (or at least, compatible types).

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Using a CTE with an UPDATE Statement in SQL Server

Posted on by Ian

In SQL Server, Common Table Expressions (CTEs) are often used for readability and simplifying complex queries. While CTEs are most commonly used when running a SELECT query, we can also use CTEs to perform updates with the UPDATE statement. This can be useful when we need to reference the same set of data multiple times or want to update records conditionally.

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Fix “No function matches the given name and argument types ‘bool_and(INTEGER)'” in DuckDB

Posted on by Ian

If you’re getting an error that reads something like “No function matches the given name and argument types ‘bool_and(INTEGER)’” in DuckDB, it’s probably because you’re passing a non-boolean value to the bool_and() function.

The bool_and() function is for use against boolean expressions, so to fix this issue, be sure that the argument you pass to the function is a boolean expression.

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Enable Vertical Query Output in DuckDB

Posted on by Ian

When using DuckDB’s command line interface (CLI), we can use the .mode command to change how query results are formatted. For example, we can output query results as a table, in CSV format, or even JSON. Another option is to output it in “line” mode, which outputs the query results vertically, as opposed to horizontally across the screen.

This article demonstrates how to enable vertical query output in the DuckDB CLI with line mode.

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How to Create a Partial Index in SQLite

Posted on by Ian

Partial indexing is a feature in many DBMSs, including SQLite, that allows developers to optimize database performance by creating indexes only for specific subsets of data. This can significantly reduce the index size and improve query speed, especially in cases where only a portion of the data is frequently queried.

In this article, we’ll look at how to create a partial index in SQLite, why it’s useful, and provide an example to illustrate its use.

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