Shulou(Shulou.com)06/01 Report--

Scene

In the query of student information, the student dormitory information is allowed to be empty, and if it is obtained, it is not empty.

Select t.girls, cs_sc_studenthostel.name as hostelname

From (

Select cs_sc_student.id as student_id

Cs_sc_student.name as studentname

Cs_sc_class.name as classname

Cs_sc_student.sc_studenthostel_id

From cs_sc_student, cs_sc_class

Where cs_sc_student.sc_class_id = cs_sc_class.id) t

Left join cs_sc_studenthostel on t.sc_studenthostel_id = cs_sc_studenthostel.id

The first step is to get the basic information of the students

(

Select cs_sc_student.id as student_id

Cs_sc_student.name as studentname

Cs_sc_class.name as classname

Cs_sc_student.sc_studenthostel_id

From cs_sc_student, cs_sc_class

Where cs_sc_student.sc_class_id = cs_sc_class.id) t

The second step is to connect to the left.

Left join cs_sc_studenthostel on t.sc_studenthostel_id = cs_sc_studenthostel.id

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