8.4.2.4 Using PROCEDURE ANALYSE
ANALYSE([
max_elements
[,max_memory
]])
PROCEDURE ANALYSE()
is deprecated as of MySQL 5.7.18, and is removed in MySQL 8.0.
ANALYSE()
examines the result from a query and returns an analysis of the results that suggests optimal data types for each column that may help reduce table sizes. To obtain this analysis, append PROCEDURE ANALYSE
to the end of a SELECT
statement:
SELECT ... FROM ... WHERE ... PROCEDURE ANALYSE([max_elements,[max_memory]])
For example:
SELECT col1, col2 FROM table1 PROCEDURE ANALYSE(10, 2000);
The results show some statistics for the values returned by the query, and propose an optimal data type for the columns. This can be helpful for checking your existing tables, or after importing new data. You may need to try different settings for the arguments so that PROCEDURE ANALYSE()
does not suggest the ENUM
data type when it is not appropriate.
The arguments are optional and are used as follows:
max_elements
(default 256) is the maximum number of distinct values thatANALYSE()
notices per column. This is used byANALYSE()
to check whether the optimal data type should be of typeENUM
; if there are more thanmax_elements
distinct values, thenENUM
is not a suggested type.max_memory
(default 8192) is the maximum amount of memory thatANALYSE()
should allocate per column while trying to find all distinct values.
A PROCEDURE
clause is not permitted in a UNION
statement.