答： Yesterday I bought a dictionary. It is a English dictionary. It is helpful to me. When I suffer from a problem about English. Then I can be reference. I like it. Also I will treasure the dictionary. 行了吗？要多少字？什么程度呀？
答： stores data about the tables and fields within the databasefor each table it stores the table name and relationships to other tablesfor each field, it records information about that fieldalso called a catalog
答： data dictionary In database management systems, a file that defines the basic organization of a database. A data dictionary contains a list of all files in the database, the number of records in each file, and the names and types of each field. Most database management systems keep the data dictionary hidden from users to prevent them from accidentally destroying its contents. Data dictionaries do not contain any actual data from the database, only bookkeeping information for managing it. Without a data dictionary, however, a database management system cannot access data from the database.
答： very good!