sqlite

database; ??? ??? ??????

explain

English [?k?splen]

vt.& vi. ?????...

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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