update statistics


Updates information about the distribution of key values in specified indexes, for all columns in an index, table, or partition, and resets the data change counters for global nonclustered indexes.


update statistics table_name
	[[partition data_partition_name] [(column_list)] |
	index_name [partition index_partition_name]] 
	[using step values]
	[with consumers = consumers][, sampling=N percent]



when used with update statistics, table_name is the name of the table with which the index is associated. table_name is required, since Transact-SQL does not require index names to be unique in a database.


is the name of the index to be updated. If an index name is not specified, the distribution statistics for all the indexes in the specified table are updated.


is the name of the partition to be updated. Statistics for each local index partition on the data partition is updated. Does not update statistics for global indexes.


is the name of the index partition to be updated.


is a comma-separated list of columns.

using step values

specifies the number of histogram steps. The default value is 20, for columns where no statistics exist. If you need to change the default for this, use sp_configure to modify the number of histogram steps parameter. If statistics for a column already exist in sysstatistics, the default value is the current number of steps.

The steps are applied to each partition of a partitioned table—for example, update statistics uses the default value of 20 steps for each data and index partition involved in the scan for updating statistics. If global statistics are generated through an index scan of a global index, then 20 steps are applied by default. If partition statistics are generated, either through a data scan or local index scan, then 20 steps are applied by default for each partition.

If the histogram steps specified through using step values is M, and the histogram tuning factor parameter is N, then update statistics uses between M and M*N steps, depending on the number of frequency cells that update statistics isolates.

with consumers = consumers

specifies the number of consumer processes to be used for a sort when column_list is provided and parallel query processing is enabled. The consumers option specifies the degree of parallelism applied to a sort performed for statistics update on a single data partition. For example, if update statistics with a column list is applied to a table with three data partitions, data from each of the three partitions is sorted separately and the consumers option is applied during each of the sort. The three sorts themselves are not performed in parallel.

with sampling = N percent

specifies the percentage of the column to be randomly sampled in order to gather statistics. The value for N is any number between 1 and 100. Sampling applies to all update statistics types:

  • update statistics table_name

  • update statistics table_name (col_name)

  • update index statistics

  • update all statistics


specifies that statistics for all columns in an index are to be updated.


Example 1

Generates statistics for the price column of the titles table:

update statistics titles (price) using 40 values

Example 2

Updates statistics on the data partition smallsales Adaptive Server creates histograms for each leading column and densities for the composite columns of each local index of the data partition. Statistics are not updated for global indexes:

update statistics titles partition smallsales

Example 3

Updates statistics on the data partition smallsales. Adaptive Server creates histograms on column col1 and creates densities for the composite columns col1 and col2:

update statistics titles partition smallsales (col1, col2)


update statistics and sampling

Sampling is not performed for leading columns of indexes. If you specify an index in update statistics, such as in the following:

update statistics table_name [index_name] with sampling = N percent

This command creates and updates statistics on the leading column of all indexes on the specified table, or the leading column of a specified index.

When you use the sampling = N percent option with the using steps value , you must specify the sampling = N percent option last:

update statistics titles (type) 
    using 40 value
    with sampling = 10 percent 

If you do not, you get an error message:

update statistics titles (type) 
    with sampling = 10 percent 
    using 40 value
Msg 156, Level 15, State 2:
Line 1:
Incorrect syntax near the keyword 'using'.

create index and stored procedures

Adaptive Server automatically recompiles stored procedures after executing update statistics statements. Although ad hoc queries that you start before executing update statistics still continue to work, they do not take advantage of the new statistics.In Adaptive Server versions 12.5 and earlier, update statistics was ignored by cached stored procedures.


ANSI SQL – Compliance level: Transact-SQL extension.


update statistics permission defaults to the table owner and is not transferable. The command can also be executed by the database owner, who can impersonate the table owner by running the setuser command.

See also

Commands delete statistics, update all statistics, update index statistics, update table statistics

Documentation Performance and Tuning Guide