Selecting a Data Type

Use the following principles to select efficient data types:

1. Select data types that facilitate data calculation.

   Generally, the calculation of integers (including common comparison calculations, such as =, >, <, ≥, ≤, and ≠ and GROUP BY) is more efficient than that of strings and floating point numbers.

2. Select data types with a short length.

   Data types with short length reduce both the data file size and the memory used for computing, improving the I/O and computing performance. For example, use SMALLINT instead of INT, and INT instead of BIGINT.

3. Use the same data type for a join.

   You are advised to use the same data type for a join. To join columns with different data types, the database needs to convert them to the same type, which leads to additional performance overheads.