Suppose I have a bunch of varchar(6000) fields in a table and want to change those to text fields. What are the ramifications of the stored procedures whose arguments are of type varchar(6000). Does each stored procedure also need those argument data types changed?
Text fields are deprecated in SQL Server 2005 and above. You should use varchar(MAX), if possible. If you expect to have more than 6000 characters passed in the arguments to your stored procedures, you will need to change them as well.
Text fields are rough to work with in SQL Server. You can't actually declare local variables of type text (except as parameters to a stored procedure) and most of the string manipulation functions no longer work on text fields.
Also if you have triggers the text fields will not appear on the INSERTED or DELETED tables.
Basically if the field is just holding data from a program and you aren't manipulating it then no big deal. But if you have stored procedures to manipulate the string then your task will be way more difficult.
As tvanfosson mentioned if you have SQL Server 2005 use VARCHAR(MAX) then you get the length of a text field with the ability to manipulate it like it is a VARCHAR.
The other answers are right, but they don't answer your question. Varchar(max) is the way to go. If you made the feilds varchar(max)/text, but kept the stored proc arguments the same, any field that came in through the stored proc would be truncated to 6000 characters. Since you say that it will never exceed that, you will be fine, until, of course, that isn't the case. It doesn't throw an error. It just truncate.
I'm not sure of the exact behavior of varchar(max) verses text, but I'm pretty sure that once you start putting a lot of them in one table, you can get some crazy performance hits. Why so many big fields in one table?
The reason for text field usage is that all of the varchar(6000) fields in one row exceed the max row length. Text fields just store a pointer in the row thus not exceeding the SQL Server max row length of 8000 something. ATM the database cannot be normalized. The data is not manipulated by the stored procedures it's just inserted, updated and deleted.
Does VARCHAR(MAX) behave like a text field and only store a pointer to the data in the row?
Related
What is the best way to store a large amount of text in a table in SQL server?
Is varchar(max) reliable?
In SQL 2005 and higher, VARCHAR(MAX) is indeed the preferred method. The TEXT type is still available, but primarily for backward compatibility with SQL 2000 and lower.
I like using VARCHAR(MAX) (or actually NVARCHAR) because it works like a standard VARCHAR field. Since it's introduction, I use it rather than TEXT fields whenever possible.
Varchar(max) is available only in SQL 2005 or later. This will store up to 2GB and can be treated as a regular varchar. Before SQL 2005, use the "text" type.
According to the text found here, varbinary(max) is the way to go. You'll be able to store approximately 2GB of data.
Split the text into chunks that your database can actually handle. And, put the split up text in another table. Use the id from the text_chunk table as text_chunk_id in your original table. You might want another column in your table to keep text that fits within your largest text data type.
CREATE TABLE text_chunk (
id NUMBER,
chunk_sequence NUMBER,
text BIGTEXT)
In a BLOB
BLOBs are very large variable binary or character data, typically documents (.txt, .doc) and pictures (.jpeg, .gif, .bmp), which can be stored in a database. In SQL Server, BLOBs can be text, ntext, or image data type, you can use the text type
text
Variable-length non-Unicode data, stored in the code page of the server, with a maximum length of 231 - 1 (2,147,483,647) characters.
Depending on your situation, a design alternative to consider is saving them as .txt file to server and save the file path to your database.
Use nvarchar(max) to store the whole chat conversation thread in a single record. Each individual text message (or block) is identified in the content text by inserting markers.
Example:
{{UserId: Date and time}}<Chat Text>.
On display time UI should be intelligent enough to understand this markers and display it correctly. This way one record should suffice for a single conversation as long as size limit is not reached.
The background of this question is that I have a column with the following definition:
FirstName VARCHAR(100).
I can insert a THAI/Chinese/European value if I change the column datatype to NVARCHAR and when inserting a value I need to Prefix it with N, as
Insert into table ([FirstName]) value(N'THAI/Chinese/European value').
Question:
There are a lot of applications that update this particular column and for me to assist this change I need to make a lot of changes to the procedures and various other application level changes. Is there a way I can make a change at the database level where I can accommodate this change.
Is there a way I can make a change at the database level where I can accommodate this change.
I don't believe there is any way to force SQL Server to handle all varchars as unicode nvarchars. They are simply different datatypes.
If you are using literals in your SQL code, you will have to use N''. Any columns, parameters, or variables that hold the data will have to be nchar/nvarchar. Your apps will all have to send unicode values to the DB.
I would search for "sql server migrate to unicode" for additional reading before you take this on.
While I agree with #TimLehner that I do not know of a way to force SQL Server to handle all varchar columns as nvarchar columns, there are a few things that could make your transition to Unicode strings in the column easier:
To support Unicode values in the column one-off or in an upgrade script, use ALTER TABLE [table] ALTER COLUMN FirstName nvarchar(100). (Of course, be sure to update your create script for [table] if applicable too - i.e. CREATE TABLE [table] (FirstName nvarchar(100)...).)
Use Unicode (i.e. N'SomeFirstName') literals where you expect to insert or set strings with Unicode characters; but continue to use non-Unicode (i.e. 'SomeFirstName') literals where you do not in transition.
Work your way up to altering procedures' parameters (i.e. from varchar to nvarchar) as needed.
Basically, ideally you would change the column and everything related to it to support Unicode at once; but you may be able to limit initial changes to application(s), procedure(s) etcetera that initially need to leverage the column's underlying Unicode support.
You could make use of a stored procedure for inserts and updates. If then the entire application uses that, you can solely update the stored procedure...
But i guess that would still require an update on all locations, so i guess this is not that much help...
Is there a datatype to pass as an out parameter to a stored procedure in Sybase that can hold indefinite amount of data? I learnt that we cannot use text as a datatype. Please help me out
Since you need more storage, you may have to logically split your input into 1 or more varchar(n).
The max size for a single varchar is the server page size (2k, 4k, 8k, or 16k depending on your environment).
How long does an nvarchar field need to be before it is better to use a text field in SQL Server? What are the general indications for using one or the other for textual content that may or may not be queried?
From what I understand, the TEXT datatype should never be used in SQL 2005+. You should start using VARCHAR(MAX) instead.
See this question about VARCHAR(MAX) vs. TEXT.
UPDATE (per comment):
This blog does a good job at explaining the advantages. Taken from it:
But the pain from using the type text comes in when trying to query against it. For example grouping by a text type is not possible.
Another downside to using text types is increased disk IO due to the fact each record now points to a blob (or file).
So basically, VARCHAR(MAX) keeps the data with the record, and gives you the ability to treat it like other VARCHAR types, like using GROUP BY and string functions (LEN, CHARINDEX, etc.).
For TEXT, you almost always have to convert it to VARCHAR to use functions against it.
But back to the root of your question regarding efficiency, I don't think it's ever more efficient to use TEXT vs. VARCHAR(MAX). Looking at this MSDN article (search for "data types"), TEXT is deprecated, and should be replaced with VARCHAR(MAX).
First of all don't use text at all. MSDN says:
ntext, text, and image data types will
be removed in a future version of
Microsoft SQL Server. Avoid using
these data types in new development
work, and plan to modify applications
that currently use them. Use
nvarchar(max), varchar(max), and
varbinary(max) instead.
varchar(max) is what you might need.
If you compare varchar(n) vs varchar(max), these are technically two different datatypes (stored differently):
varchar(n) value is always stored inside of the row. Which means it cannot be greater than max row size, and row cannot be greater than page size, which is 8K.
varchar(max) is stored outsize the row. Row has a pointer to a separate BLOB page. However, under certain condition varchar(max) can store data as a regular row, obviously it should at least fit to the row size.
So if your row is potentially greater than 8K, you have to use varchar(max). If not, using varchar(n) will likely be preferable as it is faster to retrieve in-row data vs from outside page.
MSDN says:
Use varchar(max) when the sizes of the
column data entries vary considerably,
and the size might exceed 8,000 bytes.
The main advantage of VARCHAR over TEXT is that you can run string manipulations and string functions on it. With VARCHAR(max), now you basically have an awesome large (unrestricted) variable that you can manipulate how you want..
I'm looking at an inherited SSIS package, and a stored procedure is sending records to a recordset called USER:NEW_RECORDS. It's of type Object, and the value is System.Object. It is then used for inputting that data to a SQL table. We're getting an error, because it seems that the numeric results of the stored procedure are being put in a DT_WSTR field, and then failing when it is then put into a decimal field in the database.
Most of the records are working, but one, which happens to have a longer number of decimal digits, is failing.
I want to see exactly what my SSIS recordset field types are, and probably change them, so I can force the data to be truncated properly and copied. Or, perhaps, I'm not even looking at this correctly. The data is put into the recordset using a SQL Task that executes the stored procedure.
Edit: It appears that this particular recordset is used twice, and this is the second use of it. I'm thinking that perhaps it has the data types of the first use. But I can't put a Data Viewer on a SQL Task, can I?
I am having the same trouble, so I directed the flow behind the record set into a flat file.
I did make a new recordset to use, so that the other one was not used. And while I never did figure out how to see the data, I could change the data types of the types in the parameter mapping, which was apparently what was needed. I changed a type from NUMERIC to FLOAT, and it quit complaining about some of the data.
This question may be too specific to my own problem to be of use to others. I may delete it.