The basic concept of the table
The basic memory cell, two-dimensional structure, columns row +
Data type (large type 4)
Character
char (max: 2000), nchar (max: 4000 is stored in unicode type) - fixed length
varchar (max: 4000), nvarchar (max: 8000 is stored in unicode type) - Variable length
Numeric
number (P, S), P represents the effective number of bits, S represents the number of decimal places (can be positive, 0, negative)
For example: 12.345, number (5,3)
Date type
4712 BC range indicates date January 1, 9999 to December 31, can be accurate to the second (common)
timestamp timestamp format of stored data is date, day, hour, accurate to nanoseconds (9)
other
BLOB store binary data, the maximum 4GB memory
CLOB storing character data, the maximum can be stored 4GB