Int vs. Varchar for Categorical Data: Which Improves SQL SELECT Performance?

SQL SELECT Performance: int vs. varchar for Queries

When designing a database, one crucial consideration is the data type used for different columns. The choice between int and varchar for storing categorical data, such as car makes, can significantly impact query speed.

Comparing int and varchar comparisons reveals that int comparisons are generally faster than varchar comparisons. This is due to the smaller size of int data types compared to varchar, which consumes additional space for the actual string.

This performance advantage holds true for both unindexed and indexed access. However, using an indexed int column provides the fastest execution times.

In PostgreSQL, the space usage of different data types is also relevant:

• int: 2-8 bytes per field (typically 4 bytes are sufficient)
• varchar: 4 bytes plus the actual string length

Therefore, storing car makes as an int, using an index on the column, will result in a significant speed advantage over storing the makes as a varchar, especially for large datasets.

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