# 表连接类算子（D） + `Index Join` + `EXPLAIN SELECT /*+ INL_JOIN(t1, t2) */ * FROM t1 INNER JOIN t2 ON t1.id = t2.t1_id;` ```7 +---------------------------------+-----------+-----------+------------------------------+--------------------------------------------------------------------------------+ | id | estRows | task | access object | operator info | +---------------------------------+-----------+-----------+------------------------------+--------------------------------------------------------------------------------+ | IndexJoin_10 | 180000.00 | root | | inner join, inner:IndexLookUp_9, outer key:test.t1.id, inner key:test.t2.t1_id | | ├─TableReader_28(Build) | 142020.00 | root | | data:TableFullScan_27 | | │ └─TableFullScan_27 | 142020.00 | cop[tikv] | table:t1 | keep order:false | | └─IndexLookUp_9(Probe) | 1.27 | root | | | | ├─IndexRangeScan_7(Build) | 1.27 | cop[tikv] | table:t2, index:t1_id(t1_id) | range: decided by [eq(test.t2.t1_id, test.t1.id)], keep order:false | | └─TableRowIDScan_8(Probe) | 1.27 | cop[tikv] | table:t2 | keep order:false | +---------------------------------+-----------+-----------+------------------------------+--------------------------------------------------------------------------------+ 6 rows in set (0.00 sec) ``` ------------------------------------------------------------- Index Join 又可以称为 Index Nested Loop Join，是不扫描表，只在索引上进行 nested loop 的连接方式。对于外表经过 WHERE 条件过滤后结果集较小（小于 10K 行）的场景，可以考虑使用 Index Join 的方式。