![]() It uses the allocation unit IN_ROW_Data up to 8000 bytes of data. We can store up to 8000 bytes data in this data type We can store up to 2 GB of data in this data type You can see this the estimated number of rows is 10000 while in the varchar(2000) data type it uses index seek operator and estimated number of rows is 1.96078Įstimated row size 4035 B is greater than in varchar(max) compare to the 1011 B for the varchar(2000) data typeĭifference between the varchar(max) and varchar(n) data type The estimated CPU cost is higher in the varchar(max) data type for a similar activity as of varchar(2000)įor the varchar(max) it uses clustered index scan operator and scans all records. In the following screenshot, you can see the comparison between both execution plans. It opens a window, and you can specify the path of the earlier saved execution plan. In another query execution plan, right-click and choose Compare Showplan. To compare two execution plans, save one execution plan by right click on the plan and Save Execution Plan as and provide the location to save the plan. Let’s compare the execution plan using the Compare Showplan option of SSMS. Select col1 from Employee_varchar_max where col1 like ‘xxxx%’ If we run the same query with the varchar(max) data type, it uses a clustered index scan operator, and it can be a resource-intensive operator depending upon the number of rows in the table. In the actual execution plan, we can see a non-clustered index seek operator. In the first query, we want to retrieve data from the Employee_Varchar_2000 table and get the actual execution plan. Let’s compare the execution plan of two select statements. Therefore, you should avoid creating an index with the varchar(max) data type. We can use the varchar(max) column as an included column in the index, but you cannot perform the index seek on this column. We can create an index on the key column of the table holding varchar(n) data type.Ĭolumn ‘col1’ in table ‘dbo.Employee_varchar_max’ is of a type that is invalid for use as a key column in an index. However, it is required to create an Index on the tables to improve the performance of the query. Indexes on VARCHAR(N) and VARCHAR(MAX) columnsĪs a DBA, you might not design the table. In the following screenshot, you can note the following.Įmployee_varchar_2000 insertion time 0.08 SecondsĮmployee_varchar_4500 insertion time 0.19 SecondsĮmployee_varchar_8000 insertion time 0.31 SecondsĮmployee_varchar_Max insertion time 2.72 Seconds You can use the ApexSQL Generate tool to insert the data without writing the t-SQL code for it. We want to check the data insertion time. Let’s insert 10,000 records into each of the tables we created earlier. Performance comparison between varchar(max) and varchar(n) data type If the data grows beyond the 8000 bytes, SQL Server uses LOB_DATA page for the varchar(max) data type SQL Server uses the IN_ROW_DATA page for the varchar(max) data type if the data is less than or equal to 8000 bytes. We can get the following conclusion from this. We have a pointer to this data in the IN_Row_DATA allocation unit. We get the LOB_Data allocation unit to store the data more than 8000 bytes in the Employee_Varchar_Max table. Rerun the query to check the allocation unit. It successfully inserts records in the Employee_varchar_max table. SELECT REPLICATE ( CONVERT ( VARCHAR ( max ), 'x' ), 8001 ) We will also create a table with a varchar(max) data type. Let’s create a few sample tables with different size in varchar data type. You might think of using the varchar(max) data type to store 2 GB data to resolve the string truncation issues. Due to this, we can store up to 8000 bytes of data using varchar (8000) data type. Apart from this, page also contains row overhead and row offset and leaves 8000 bytes to use for data storage. We can store 8096 bytes ( 8192-96 bytes) for data in SQL Server. On a page, SQL Server uses 96 bytes for the page header. The page size is 8 KB (8192 byes) in SQL Server, and it is fixed. As you might be aware that the basic unit of storage in SQL Server is a page. All these data types can store data up to 2 GB. It replaces the large blob object Text, NText and Image data types. The SQL Server 2005 introduced this varchar(max) data type. ![]() Overview of the VARCHAR(max) SQL Server Data Type We will discuss the use of varchar max and its implications, comparison with the varchar (n) data type in this article. In order to gain understanding about this data type, read SQL varchar(n) article. We can define a specific range for the varchar (n) data type, and it is the recommended way to do so. Is it a good practice to use varchar(max) for each usage? We might not be sure about the data length, or we want to eliminate the string or binary truncation error. ![]() I have seen that SQL developers use varchar(max) data while designing the tables or temporary tables.
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