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This article mainly explains the "ADO tool query how to use", the article explains the content is simple and clear, easy to learn and understand, the following please follow the editor's ideas slowly in depth, together to study and learn "ADO tool query how to use" it!

COM does not resolve such names until it is officially operational. Do not return a recordset unless absolutely necessary. When the query being executed returns a record, the ADO tool constructs a Recordset object, more colorful login and personalization services, and better data access and synchronization.

Recordset objects are expensive, so you should avoid using Recordset objects as much as possible. The ADO tool notes that sometimes executing a query returns a result, but not a record. For example, you can return an integer value through the Return Status parameter. In addition, you can return the Output parameter instead of the recordset that needs to construct the Recordset object. SQL Server allows you to return up to 1000 Output parameters.

Whenever possible, replace the updatable Recordset cursor with action queries (INSERT,UPDATE,DELETE and the stored procedures that perform these operations). At this point, the ADO tool you should use the Execute method and its adExecuteNoRecords option to make sure that ADO knows that the query does not need to construct a Recordset object.

Do not request the server to sort unless necessary. The ADO tool in most cases, for a moderately sized Recordset object, sorting will be faster when it is sent to the client. In addition, if you ask the ADO client to sort the records in Recordset, the client application can sort in the order selected by the user, thus increasing flexibility. Understand the structure of the index before writing the query. By creating appropriate indexes and adjusting the syntax of the query to take advantage of these indexes, you will be able to improve the speed of record extraction. Query Analyzer can help you decide whether it is necessary to add more indexes.

Do not return too many records at once. In many cases, too large a recordset seriously affects the performance of the application. Return only the records you need right now, the ADO tool. If the client needs more records, it can be extracted at any time later. Limit the scope of the query through the WHERE clause with parameters, or the flexible use of TOP N queries. Do not return too many columns. Avoid using SELECT *. The SELECT * statement tells SQL Server to return all columns, no matter how many columns actually exist.

Select only the columns you need so that when someone adds more columns to the table, you don't get a surprisingly large result set. Avoid using cursors. ADO tool if you must use cursors, do not use cursor types that require more resources than necessary. Do not require cursors to provide scrolling, update, and data buffering capabilities if not necessary.

Tell the ADO tool exactly what you want it to do. When opening Recordset or constructing a Command object, don't forget to set the CommandType option. It avoids ADO "guessing" your intentions, and you will be able to reduce communication with the server and make the code more stable. In addition, learn to use diagnostic tools to determine how much time is taken by code and application code running on the server-and where that time is spent. SQL Server Profiler is a valuable tool in this regard.

It can clarify what your code is asking the server to do and can highlight it in hastily constructed queries or for misselected command properties. In addition, the ADO tool Query Analyzer can also graphically show how SQL Server will execute the query, put forward suggestions to improve the query, and help you adjust the query. Query Analyzer can even implement its recommendations (for example, adding or deleting indexes), which can be done at the click of a button.

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