Choose any three.
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SQLite里的SQL
SQL As Understood By SQLite
EXPLAIN
SQL语句都可以前缀一个"EXPLAIN"关键词或者"EXPLAIN QUERY PLAN"短语。这个修改会使SQL语句返回不包含前缀时该语句如果执行的信息。
An SQL statement can be preceded by the keyword "EXPLAIN" or
by the phrase "EXPLAIN QUERY PLAN". Either modification causes the
SQL statement to behave as a query and to return information about
how the SQL statement would have operated if the EXPLAIN keyword or
phrase had been omitted.
EXPLAIN 和 EXPLAIN QUERY PLAN的输出结果只是为了交互分析和解决故障用的。每个SQLite发行版都会对输出的具体格式做出一定改动。当准确行为可能发生变化或者只有部分文档时应用不应当使用EXPLAIN 或 EXPLAIN QUERY PLAN。
The output from EXPLAIN and EXPLAIN QUERY PLAN is intended for
interactive analysis and troubleshooting only. The details of the
output format are subject to change from one release of SQLite to the next.
Applications should not use EXPLAIN or EXPLAIN QUERY PLAN since
their exact behavior is variable and only partially documented.
当只使用EXPLAIN关键词时，该语句返回的是执行不包含EXPLAIN的SQL命令的虚拟机指令列表。如果使用EXPLAIN QUERY PLAN短语，则返回的是该查询将要使用的查询计划的高层信息表述。
When the EXPLAIN keyword appears by itself it causes the statement
to behave as a query that returns the sequence of
virtual machine instructions it would have used to execute the command had
the EXPLAIN keyword not been present. When the EXPLAIN QUERY PLAN phrase
appears, the statement returns high-level information regarding the query
plan that would have been used.
EXPLAIN QUERY PLAN命令更详细的信息参见这里。
The EXPLAIN QUERY PLAN command is described in
more detail here.