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。
If both values are of type CHAR, the result is also of type CHAR.
如果两个值都是char类型，结果还是char类型。
Thus, array (pointer (char), 4) is the type of arrays of 4 Pointers to char.
因此y的类型就是有四个元素、这些元素指向char类型的指针数组。
The unsigned char data type, and byte data type will yield incorrect results and act as though they are signed types i. e. type char.
无符号字符数据类型和二进制数据类型将产生错误的计算结果，会当成有符号的数据类型进行计算。
The unsigned char data type, and byte data type will yield incorrect results and act as though they are signed types i. e. type char.
无符号字符数据类型和二进制数据类型将产生错误的计算结果，会当成有符号的数据类型进行计算。
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