We will use this routine to execute SQL statements against XL and see what it does and doesn't support. Start by pressing CTRL-G to get to Windows immediately. Copy this to the window immediately.
Test "CREATE TABLE Persons (PersonID int, LastName varchar(255), FirstName varchar(255), Address varchar(255), City varchar(255))"
Click to the right of the line and press ENTER. That created a M?i Workbooktrong C: \ du?c g?i là Test.xls và dã thêm m?t B?ng tính có tên Ngu?i v?i nam tiêu d? c?t (Ð?t cu?c b?n không bi?t VBA c?a XL có th? làm du?c!) XL dã th?c hi?n chính xác nh?ng gì DBMS nên làm. Vì v?y, hãy xem nh?ng gì XL khác có th? làm nhu m?t DBMS. Hãy th? dòng này:
Test "CREATE TABLE States (Code varchar, Description varchar)"
That added another Worksheet to Test.xls called States with two column headings. Wow - XL looks like a database - right? Let's see. Try this:
Test "INSERT INTO Persons VALUES (1,'Hatmaker','Craig','100 Main St', 'Anytown')"
That has added a record to the People spreadsheet - just like a database. Please continue. Type:
Test "DELETE FROM Persons Where PersonID = 1"
That happens with the " Data type doesn't match in criteria expression" l?i. Huh? The error says that XL thinks PersonID is no longer a number. See if it thinks it is a character. Type:
Test "DELETE FROM Persons Where PersonID = '1'"
XL reports " Delete data in the linked table not supported by this ISAM ", which means that XL simply does not support basic database operations like DELETE. But hey! We know we can delete records in XL. Give what? And to be honest, I have no idea. All I know is that SQL is the standard for database manipulation, but XL refuses to let SQL perform this basic operation. Go on. To try on:
Test "ALTER TABLE Persons ADD DateOfBirth date"
This is supposed to add a column. XL reports "Invalid activity ". Again, we can do that through the XL's GUI but XL rejects SQL.
Test "CREATE INDEX PersonsByName ON Persons (PersonID)"
XL reports "Unsupported operation for this type of audience ". An Index provides a code-based, somewhat similar approach to the INDEX function INDEX . Nhung cung gi?ng nhu b?t k? ch?c nang, cácINDEX ch?c nang of XL returns the result. An Index co s? d? li?u nào not. It is an object that holds a pointer to all records (not just one) sorted by speed based on the criteria in the CREATE INDEX statement . There is no Index v?t in XL and thus this SQL operation fails.
Test "CREATE VIEW PersonsByName as SELECT LastName FROM Persons"
This is supposed to create an object that only displays the LastNamecánh d?ng. Think of this as hiding all columns except LastName . This is useful for security but fails with the message " Operation not supported for this type of object ". And think about security:
Test "GRANT SELECT ON Persons TO [Craig Hatmaker]"
This is supposed to grant me authorization for the People table. XL reports invalid SQL Statement; Expect 'DELETE', 'CONFIRM', 'PROCEDURE', 'SELECT' or 'UPDATE' unlike DBMS, XL does not have user-based security.
Explore this strange territory alone. Try any SQL statement using routine check and discover exactly what XL can and can not do as a DBMS ..
Em thông minh theo ngày, hôm nay cuối tuần nên Pó tay hihi
