مشاركة عبر

  • مقالة

WRITETEXT (Transact-SQL)

Permits minimally logged, interactive updating of an existing text, ntext, or image column. WRITETEXT overwrites any existing data in the column it affects. WRITETEXT cannot be used on text, ntext, and image columns in views.

Important

This feature will be removed in a future version of Microsoft SQL Server. Avoid using this feature in new development work, and plan to modify applications that currently use this feature. Use the large-value data types and the .WRITE clause of the UPDATE statement instead.

Topic link iconTransact-SQL Syntax Conventions

Syntax

WRITETEXT { table.column text_ptr }
  [ WITH LOG ] { data }

Arguments

  • table**.**column
    Is the name of the table and text, ntext, or image column to update. Table and column names must comply with the rules for identifiers. Specifying the database name and owner names is optional.

  • text_ptr
    Is a value that stores the pointer to the text, ntext, or image data. text_ptr must be binary(16).To create a text pointer, execute an INSERT or UPDATE statement with data that is not null for the text, ntext, or image column.

  • WITH LOG
    Ignored by SQL Server. Logging is determined by the recovery model in effect for the database.

  • data
    Is the actual text, ntext or image data to store. data can be a literal or a parameter. The maximum length of text that can be inserted interactively with WRITETEXT is approximately 120 KB for text, ntext, and image data.

Remarks

Use WRITETEXT to replace text, ntext, and image data and UPDATETEXT to modify text, ntext, and image data. UPDATETEXT is more flexible because it changes only a part of a text, ntext, or image column instead of the whole column.

For best performance we recommend that text, ntext, and image data be inserted or updated in chunk sizes that are multiples of 8040 bytes.

If the database recovery model is simple or bulk-logged, text, ntext, and image operations that use WRITETEXT are minimally logged operations when new data is inserted or appended. For more information, see Operations That Can Be Minimally Logged.

Note

Minimal logging is not used when existing values are updated.

For WRITETEXT to work correctly, the column must already contain a valid text pointer.

If the table does not have in row text, SQL Server saves space by not initializing text columns when explicit or implicit null values are added in text columns with INSERT, and no text pointer can be obtained for such nulls. To initialize text columns to NULL, use the UPDATE statement. If the table has in row text, you do not have to initialize the text column for nulls and you can always get a text pointer.

The ODBC SQLPutData function is faster and uses less dynamic memory than WRITETEXT. This function can insert up to 2 gigabytes of text, ntext, or image data.

In SQL Server, in row text pointers to text, ntext, or image data may exist but may not be valid. For information about the text in row option, see sp_tableoption (Transact-SQL). For information about invalidating text pointers, see sp_invalidate_textptr (Transact-SQL).

Permissions

Requires UPDATE permission on the specified table. Permission is transferable when UPDATE permission is transferred.

Examples

The following example puts the text pointer into the local variable @ptrval, and then WRITETEXT places the new text string into the row pointed to by @ptrval.

Note

To run this example, you must install the pubs sample database. For information on how to install the pubs sample database, see Downloading Northwind and pubs Sample Databases.

USE pubs;
GO
ALTER DATABASE pubs SET RECOVERY SIMPLE;
GO
DECLARE @ptrval binary(16);
SELECT @ptrval = TEXTPTR(pr_info) 
FROM pub_info pr, publishers p
WHERE p.pub_id = pr.pub_id 
   AND p.pub_name = 'New Moon Books'
WRITETEXT pub_info.pr_info @ptrval 'New Moon Books (NMB) has just released another top ten publication. With the latest publication this makes NMB the hottest new publisher of the year!';
GO
ALTER DATABASE pubs SET RECOVERY SIMPLE;
GO