Question

我有两张桌子＆＃34; Student_Info表＆＃34;和＆＃34; Training_Status表＆＃34;

Student_Info包含有关姓名，学生的groupId，学生的组卷数，年龄等的信息。 Training_Status表包含不同学生的培训状态

表的结构如下：

Student_Info表

groupId    GroupRollNo     Name      Age     Level
- - - - - - - - - - - - - - - -  - - -  - -  -  - -  
G1             1           Sam       24        4 
G1             2           David     25        2 
G1             3           Robin     26        3 
G1             4           John      28        4 
G2             1           Harry     26        3 
G2             2           Jerry     28        4 
G3             1           Michel    28        3
G3             2           Jerry     28        4 
G4             1           Michel    28        3

学生分为G1，G2，G3组同一组中的学生不能拥有相同的GroupRollNo。但来自不同群体的学生可以拥有相同的GroupRollNo。

Training_Status表

groupId     GroupRollNo    TrainingStatus
- - - - - - - - - - - - - - - - - - - - - 
 G1             2            InProgress
 G1             3            OnHold
 G3             1            InProgress
 G3             2            Completed

随着学生的培训开始，参赛作品进入＆＃34; Training_Status Table＆＃34; with groupId和GroupRollNo以及Training Status。并且表格更新了培训状态（OnHold，已完成）

考虑情景

Student_Info表中有100名学生分为不同的组。（比如G1，G2，G3）。 Training_Status Table只有10个条目（只有那些已经开始培训的学生）来自不同的当前状态组。

我需要从特定组中获取所有学生的培训状态，并提供两个表中学生的详细信息。
就像我需要获取G1（第1组）所有学生的培训状态，并提供来自Sqlite数据库查询的学生的完整详细信息。

预期的查询结果

groupId    GroupRollNo     Name        Age     Level    TrainingStatus
- - - - - - - - - - - - - - - -  - - -  - -  -  - - - - - - - - - - - - -
 G1             1          Sam         24        4      NULL(means training not started)
 G1             2          David       25        2      InProgress
 G1             3          Robin       26        3      OnHold
 G1             4          John        28        4      NULL(means training not started)

我应该写什么sqlite查询因此我从两个表中获得所需格式的结果。

Answer 1

我刚刚创建了一个示例来说明如何根据您的数据执行此操作：

-- Set up sqlite
.mode column
.headers ON
--
DROP TABLE IF EXISTS Student_Id;
CREATE TABLE Student_Id (
   groupId TEXT,
   GroupRollNo INTEGER,
   Name TEXT,
   Age INTEGER,
   Level INTEGER,
   UNIQUE(groupId, GroupRollNo));
--
DROP TABLE IF EXISTS Training_Status;
CREATE TABLE Training_Status (
   groupId TEXT,
   GroupRollNo INTEGER,
   TrainingStatus TEXT,
   UNIQUE(groupId, GroupRollNo));
--
-- Create Data
INSERT INTO Student_Id (groupId, GroupRollNo, Name, Age, Level) VALUES("G1", 1, "Sam", 24, 4);
INSERT INTO Student_Id (groupId, GroupRollNo, Name, Age, Level) VALUES("G1", 2, "Sam", 24, 4);
INSERT INTO Student_Id (groupId, GroupRollNo, Name, Age, Level) VALUES("G1", 3, "Sam", 24, 4);
INSERT INTO Student_Id (groupId, GroupRollNo, Name, Age, Level) VALUES("G1", 4, "Sam", 24, 4);
INSERT INTO Student_Id (groupId, GroupRollNo, Name, Age, Level) VALUES("G2", 1, "Sam", 24, 4);
INSERT INTO Student_Id (groupId, GroupRollNo, Name, Age, Level) VALUES("G2", 2, "Sam", 24, 4);
INSERT INTO Student_Id (groupId, GroupRollNo, Name, Age, Level) VALUES("G3", 1, "Sam", 24, 4);
INSERT INTO Student_Id (groupId, GroupRollNo, Name, Age, Level) VALUES("G3", 2, "Sam", 24, 4);
INSERT INTO Student_Id (groupId, GroupRollNo, Name, Age, Level) VALUES("G4", 1, "Sam", 24, 4);
INSERT INTO Student_Id (groupId, GroupRollNo, Name, Age, Level) VALUES("G4", 2, "Sam", 24, 4);
-- 2nd Table
INSERT INTO Training_Status (groupId, GroupRollNo, TrainingStatus) VALUES("G1", 2, "InProgress");
INSERT INTO Training_Status (groupId, GroupRollNo, TrainingStatus) VALUES("G1", 3, "OnHold");
INSERT INTO Training_Status (groupId, GroupRollNo, TrainingStatus) VALUES("G3", 1, "InProgress");
INSERT INTO Training_Status (groupId, GroupRollNo, TrainingStatus) VALUES("G3", 2, "Completed");

查询部分：

-- Check data
SELECT * FROM Student_Id;
SELECT * FROM Training_Status;

-- 1.- Query (inner JOIN: only records that are on both tables)
SELECT t1.groupId AS groupId, t1.GroupRollNo AS GroupRollNo, t1.Name AS Name, 
   t1.Age AS Age, t1.Level AS Level, t2.TrainingStatus AS TrainingStatus
FROM Student_Id AS t1, Training_Status AS t2
WHERE t1.groupID = t2.groupId AND t1.GroupRollNo = t2.GroupRollNo AND t1.groupId = "G1"
ORDER BY t1.groupId, t1.GroupRollNo;

-- 2.- Query (outer join: Both tables are combined together showing all records)
SELECT t1.groupId AS groupId, t1.GroupRollNo AS GroupRollNo, t1.Name AS Name, 
   t1.Age AS Age, t1.Level AS Level, t2.TrainingStatus AS TrainingStatus
FROM Student_Id AS t1 LEFT JOIN Training_Status AS t2
ON t1.groupID = t2.groupId AND t1.GroupRollNo = t2.GroupRollNo
WHERE t1.groupId = "G1"
ORDER BY t1.groupId, t1.GroupRollNo;

-- 3.- Query for NOT NULL (outer join: Both tables are combined together showing all records)
SELECT t1.groupId AS groupId, t1.GroupRollNo AS GroupRollNo, t1.Name AS Name, 
   t1.Age AS Age, t1.Level AS Level, t2.TrainingStatus AS TrainingStatus
FROM Student_Id AS t1 LEFT JOIN Training_Status AS t2
ON t1.groupID = t2.groupId AND t1.GroupRollNo = t2.GroupRollNo
WHERE t1.groupId = "G1" AND t2.TrainingStatus IS NOT NULL
ORDER BY t1.groupId, t1.GroupRollNo;

-- 4.- Query for NULL (outer join: Both tables are combined together showing all records)
SELECT t1.groupId AS groupId, t1.GroupRollNo AS GroupRollNo, t1.Name AS Name, 
   t1.Age AS Age, t1.Level AS Level, typeof(t2.TrainingStatus) AS TrainingStatus
FROM Student_Id AS t1 LEFT JOIN Training_Status AS t2
ON t1.groupID = t2.groupId AND t1.GroupRollNo = t2.GroupRollNo
WHERE t1.groupId = "G1" AND t2.TrainingStatus IS NULL
ORDER BY t1.groupId, t1.GroupRollNo;

请注意以下事项：

UNIQUE（...）约束将阻止具有相同groupId和GroupRollNo的两个条目。

使用显式列groupId和GroupRollNo查询联合两个表。

需要使用IS NULL而不是= NULL来查询NULL值。

从2个表中选择查询获取数据：sqlite

1 个答案: