Điều này mang đến một màn hình điều hành hộp thoại mới. Như bạn có thể thấy trong hình 7-60, không chỉ bạn có thể gửi e-mail, nhưng bạn cũng có thể làm một hệ thống gửi tin nhắn, cung cấp được kích hoạt trên mạng của bạn, và ping một máy nhắn tin. Nhập các chi tiết như thể hiện trong hình 7-60. | 290 CHAPTER 8 WORKING WITH THE DATA Understand the dangers when transactions are nested Know the syntax for the DELETE command Know how to use this command in T-SQL Are aware of the pitfalls of the TRUNCATE command First of all let s take a look at the syntax for the UPDATE command. The UPDATE Command The UPDATE command will update columns of information on rows within a single table returned from a query that can include selection and join criteria. The syntax of the UPDATE command has similarities to the SELECT command which makes sense as it has to look for specific rows to update just as the SELECT statement looks for rows to retrieve. You will also find that before doing updates especially more complex updates you need to build up a SELECT statement first and then transfer the JOIN and WHERE details in to the UPDATE statement. The syntax that follows is in its simplest form. Once you become more experienced the UPDATE command can become just as complex and versatile as the SELECT statement. UPDATE TOP expression PERCENT server_name . database_name . schema_name . database_name . schema_name . schema_name . table_or_viewname SET column_name expression DEFAULT NULL column_name .WRITE expression @Offset @Length @variable expression @variable column expression .n .n FROM table_source .n WHERE search_condition The first set of options we know from the SELECT statement. The tablename clause is simply the name of the table on which to perform the UPDATE. Moving on to the next line of the syntax we reach the SET clause. It is in this clause that any updates to a column take place. One or more columns can be updated at any one time but each column to be updated must be separated by a comma. When updating a column there are four choices that can be made for data updates. This can be through a direct value setting a section of a value setting providing that the recipient column is varchar nvarchar or varbinary the value from a variable or a value from another column even
