Subversion - > Git迁移：git clone没有完全克隆？(Subversion -> Git migration: git clone not making a full clone?)

 使用UNION ALL （ 实际上只有UNION会这样做，因为学生没有头衔 ）。 SInce表STUDENT没有标题，您需要有一个带有别名title的空列，以便它与列数相匹配。 如果您没有为标题添加额外的列，则会出现错误消息 
 
The used SELECT statements have a different number of columns...
 
 完整查询， 
 
SELECT  schoolid, 
        instructorusername username, 
        instructorfirstname firstName, 
        instructorlastname lastName,
        instructortitle title,
        level
FROM    instructors
UNION 
SELECT  schoolid, 
        studentusername username, 
        studentfirstname firstName, 
        studentlastname lastName,
        '' title,
        level
FROM    students
 
 
 
 SQLFiddle演示 
 

use UNION ALL (actually just UNION will do since students have no title). SInce table STUDENT doesn't have title, you need to have an empty column with alias title so it will match the column count. If you don't add extra column for title, you will have error message 
 
The used SELECT statements have a different number of columns...
 
Full Query,
 
SELECT  schoolid, 
        instructorusername username, 
        instructorfirstname firstName, 
        instructorlastname lastName,
        instructortitle title,
        level
FROM    instructors
UNION 
SELECT  schoolid, 
        studentusername username, 
        studentfirstname firstName, 
        studentlastname lastName,
        '' title,
        level
FROM    students
 
 
 
SQLFiddle Demo