For our example, item_id is a char column that stores only numeric characters, as we indicate in the following statement.
对于我们的例子，item_id是一个char列，它只存储数字字符，如以下语句所示。
In the first query, the filtering predicate is expressed on the CHAR column "Zip" generated by the XMLTABLE function.
在第一个查询中，过滤谓词是在由xmltable函数生成的char列“Zip”上表达的。
The CHAR data type provides a performance boost because the database knows exactly how big every CHAR column will be and can make certain performance optimizations when reading or writing the data.
CHAR数据类型有助于性能提高，因为数据库确切地知道每个char列有多大，所以在读写数据时就可以执行某种性能优化。
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