Description
The EXPLAIN command offers insight into the
internal database operation. Placing EXPLAIN in front of any SQL statement (other
than itself) returns information about how SQLite would execute
the given SQL statement. The SQL statement is not actually
executed.
By itself, EXPLAIN will return a result set that describes
the internal VDBE instruction sequence used to execute the
provided SQL statement. A fair amount of knowledge is required
to understand the
output.
The full EXPLAIN QUERY PLAN variant will return a
high-level summary of the query plan using English-like
explanations of how the query will be assembled and if data will
be accessed by a table scan or by index lookup. The EXPLAIN QUERY PLAN command is
most useful for tuning SELECT
statements and adjusting index placement.
These commands exist to help database administrators and developers understand how SQLite is processing SQL commands. They are designed for interactive tuning and adjustments. It is not recommended that applications programmatically query or utilize this data, as both the data and the format may change from one version of SQLite to the next.