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Data Wrangling with SQL
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Each value stored in a database has a fixed data type that defines its properties, storage size, and what data size that variable can hold. Every time we perform data manipulation in SQL, we need to ensure that the data type is compatible with the manipulation operation.
Data types are categorized into the following six types, which are explained in more detail here:
Figure 3.1 – SQL data types
Overall, there are four different numerical data types that differ by the level or type of information we are trying to store, such as the number of characters/decimal points.
Numbers such as phone numbers and customer IDs use the nominal data type because number operations such as add, subtract, and compare cannot be performed on this data type. They are for informational purposes rather than analysis. Nominal data is also called qualitative or categorical.
Note
Only calculations based...