sqlite
database; ??? ??? ??????
explain
English [?k?splen]
vt.& vi. ?????...
vi.????, ????, ?????
SQLite ?? ?? ???
??: SQLite ? ?? "EXPLAIN" ???? "EXPLAIN QUERY PLAN" ??? ???? ???? ?? ??? ??? ? ????. EXPLAIN ???? ??? ??? ?? ???? SQLite ?? ?? ??? SQLite ?? ?? ??? ?? ??? ???? ???. EXPLAIN ? EXPLAIN QUERY PLAN? ??? ??? ?? ? ?? ???? ?????. ?? ??? ?? ??? SQLite ??? ?? ?? ? ????. ??? ??? ????? ?????? ????? ??????? EXPLAIN ?? EXPLAIN QUERY PLAN? ????? ? ???.
??: EXPLAIN ??? ??? ????.
EXPLAIN [SQLite Query]
EXPLAIN QUERY PLAN ??? ??? ????.
EXPLAIN QUERY PLAN [SQLite Query]
SQLite ?? ?? ?
假設(shè) COMPANY 表有以下記錄: ID NAME AGE ADDRESS SALARY ---------- ---------- ---------- ---------- ---------- 1 Paul 32 California 20000.0 2 Allen 25 Texas 15000.0 3 Teddy 23 Norway 20000.0 4 Mark 25 Rich-Mond 65000.0 5 David 27 Texas 85000.0 6 Kim 22 South-Hall 45000.0 7 James 24 Houston 10000.0 現(xiàn)在,讓我們檢查 SELECT 語句中的 Explain 使用: sqlite> EXPLAIN SELECT * FROM COMPANY WHERE Salary >= 20000; 這將產(chǎn)生以下結(jié)果: addr opcode p1 p2 p3 ---------- ---------- ---------- ---------- ---------- 0 Goto 0 19 1 Integer 0 0 2 OpenRead 0 8 3 SetNumColu 0 5 4 Rewind 0 17 5 Column 0 4 6 RealAffini 0 0 7 Integer 20000 0 8 Lt 357 16 collseq(BI 9 Rowid 0 0 10 Column 0 1 11 Column 0 2 12 Column 0 3 13 Column 0 4 14 RealAffini 0 0 15 Callback 5 0 16 Next 0 5 17 Close 0 0 18 Halt 0 0 19 Transactio 0 0 20 VerifyCook 0 38 21 Goto 0 1 22 Noop 0 0 現(xiàn)在,讓我們檢查 SELECT 語句中的 Explain Query Plan 使用: SQLite> EXPLAIN QUERY PLAN SELECT * FROM COMPANY WHERE Salary >= 20000; order from detail ---------- ---------- ------------- 0 0 TABLE COMPANY