You can also use the EXPLAIN statement for joins.
· Display of the order in which the tables are processed when the SELECT statement is executed
· Display of whether the join column values of the old temporary results table can be accessed directly or through an inversion to the rows of a new table
· Display of the strategy used to search in the new table, if the rows of this table cannot be accessed directly or using an inversion
EXEC SQL EXPLAIN SELECT one
.key ten1
.keyft1, ten2
.keyft2
FROM one, ten1, ten2
WHERE ten1.keyft1 < 100
AND ten1.ft1 = one.keyf
AND one.indf
= ten2.keyft2
AND ten2.keyft2 < 100;
This EXPLAIN statement produces the following output:
TABLE NAME |
COLUMN_ |
STRATEGY |
PAGE COUNT |
TEN1 ONE TEN2 |
KEF KEYFT2 |
RANGE CONDITION FOR KEY COLUMN JOIN VIA KEY COLUMN RESULT IS COPIED, COSTVALUE IS |
1250 125 1463 97 |