sql功能与特性（SQL functions and features）.doc

sql功能与特性（SQL functions and features） SQL functions and features In fact, in the previous article, some of the basic functions of the SQL command have been mentioned. However, by SQL commands, program designers, or database administrators (DBA) can: (I) form a database. (including the space you can use to set up the table) (two) change the database system environment settings. (three) grant access to a user for a database or table. (four) index values for database tables. (five) modify the database table structure. (new, deleted, or modified table fields) (six) new data is built to the database. (seven) delete data from the database. (eight) modify the data of the database. (nine) query the data of the database. These are the things that can be done through the SQL command. Does it seem to be much more functional than the two word query? Classification of SQL syntax In fact, the SQL command is not very much, but want to use SQL but also need only reach the acme of perfection, just a few orders is enough, because the SQL command is based on relational database established by the grammatical narrative, so SQL plays in this database function is very strong, as will be directed at the VB in common use SQL basic commands to introduce grammar classification. Before you specify the command of SQL and use the syntax, the following categories of SQL are made, roughly the type used by the SQL syntax, which is said to be included in these categories. First class, attribute word (Predicates) In the SQL command, the way to indicate the record to be selected. Such as ALL, TOP and DISTINCT and so on. Second categories and declarations (Declaration) Declare a name and data type for SQL, Parameter, or Parameter Query, such as PARAMETERS statements, and so forth. The third class, the conditional clause (Clause) In SQL queries, you use some expressions to define query conditions to narrow down the search A range, such as WHERE. Fourth classes, operators (Operator) and operands (Operati