Here is an example when left outer join makes the difference. Example
could seem very artificial but SQLite should count on any possible
usage.
sqlite> create table Employee (name int);
sqlite> create table Uniform (employeename, inseam, constraint ue
unique (employeename));
sqlite> insert into employee values ("Joe");
sqlite> insert into employee values ("Steve");
sqlite> insert into Uniform values ("Joe", 77);
sqlite> insert into employee values (1);
sqlite> insert into Uniform values (1, 77);
sqlite> insert into Uniform values ("1", 77);
sqlite> select Name from Employee left outer join Uniform on
Employee.name=Uniform.employeename;
Joe
Steve
1
1
sqlite> select Name from Employee;
Joe
Steve
1
sqlite>
Pavel
On Wed, May 30, 2012 at 1:15 PM, Charles Samuels <char...@cariden.com> wrote:
> On Wednesday, May 30, 2012 10:14:22 f.h. Charles Samuels wrote:
>> sqlite> select Name from Employee join Uniform on
>> Employee.name=Uniform.employeename;
>> Joe
>> Dave
>> sqlite> explain query plan select Name from Employee join Uniform on
>> Employee.name=Uniform.employeename;
>> 0|0|0|SCAN TABLE Employee (~1000000 rows)
>> 0|1|1|SEARCH TABLE Uniform USING COVERING INDEX sqlite_autoindex_Uniform_1
>> (employeename=?) (~1 rows)
>
> I mean "left outer join" here!
>
> sqlite> select Name from Employee left outer join Uniform on
> Employee.name=Uniform.employeename;
> Joe
> Steve
> Eric
> Dave
> sqlite> explain query plan select Name from Employee left outer join Uniform
> on Employee.name=Uniform.employeename;
> 0|0|0|SCAN TABLE Employee (~1000000 rows)
> 0|1|1|SEARCH TABLE Uniform USING COVERING INDEX sqlite_autoindex_Uniform_1
> (employeename=?) (~1 rows)
>
> Charles
> (can never proofread enough.)
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