根据给定的信息，我们可以整理出以下几个重要的SQL知识点及相关示例：
### 1. 删除重复记录中的非最小ID
**需求**: 删除表`Table_1`中具有相同`name`值的记录，但只保留每组中`id`最小的记录。
**SQL 代码**:
```sql
DELETE FROM Table_1
WHERE id NOT IN (SELECT MIN(id)
FROM Table_1
GROUP BY name);
```
### 2. 查询平均分低于60分的学生数量超过2个的情况
**需求**: 需要查询出平均分数低于60分且这样的学生数量超过2个的情况。
**SQL 代码**:
```sql
SELECT L.SID, AVG(L.Score) AS AverageScore
FROM Link L
WHERE L.SID IN (
SELECT S.SID
FROM (
SELECT SID, COUNT(SID) AS Num
FROM Link
WHERE Score < 60
GROUP BY SID
) S
WHERE Num >= 2
)
GROUP BY L.SID;
```
### 3. 合并两张表并计算输入输出总和
**需求**: 给定两张表`table1`和`table2`，需要合并这两张表，并计算每个产品的输入输出总量。
**SQL 代码**:
```sql
SELECT A.PID, A.Product, SUM(A.InputNum) AS InputNum, SUM(A.OutputNum) AS OutputNum
FROM (
SELECT P1.PID, P1.Product, P1.InputNum, 0 AS OutputNum
FROM Product1 P1
UNION ALL
SELECT P2.PID, P2.Product, 0 AS InputNum, P2.OutputNum
FROM Product2 P2
) A
GROUP BY A.PID, A.Product;
```
### 4. 比较两个课程的成绩
**需求**: 给定学号（SID）、课程编号（COURSEID）和成绩（SCORE），需要查询出第1门课程成绩高于第2门课程成绩的学生情况。
**SQL 代码 1** (使用窗口函数):
```sql
WITH A AS (
SELECT L.SID, L.COURSEID, L.Score AS Score1, 0 AS Score2
FROM Link L
WHERE L.CourseID = 1
),
B AS (
SELECT L.SID, L.COURSEID, 0 AS Score1, L.Score AS Score2
FROM Link L
WHERE L.CourseID = 2
)
SELECT D.*
FROM (
SELECT C.SID, SUM(SCORE1) AS Score1, SUM(SCORE2) AS Score2
FROM (
SELECT * FROM A
UNION
SELECT * FROM B
) C
GROUP BY C.SID
) D
WHERE D.Score1 > D.Score2;
```
**SQL 代码 2** (使用子查询):
```sql
SELECT A.SID, A.Score AS Course1Score, B.Score AS Course2Score
FROM (
SELECT SID, Score
FROM Link
WHERE CourseID = 1
) A
JOIN (
SELECT SID, Score
FROM Link
WHERE CourseID = 2
) B ON A.SID = B.SID
WHERE A.Score > B.Score;
```
### 5. 更新表B中的b2列使其与表A中的a2列相等，其中A.a1=B.b1
**需求**: 更新表B中的`b2`列，使其等于表A中对应的`a2`值，其中`A.a1=B.b1`。
**SQL 代码**:
```sql
UPDATE B
SET B.b2 = A.a2
FROM A
WHERE A.a1 = B.b1;
```
### 6. 使用窗口函数生成行号、排名等
**需求**: 给定表`A`，使用窗口函数生成行号、排名等。
**SQL 代码 1** (使用窗口函数):
```sql
SELECT ROW_NUMBER() OVER (ORDER BY a1 ASC) AS RowID,
RANK() OVER (ORDER BY a1 ASC) AS RankX,
DENSE_RANK() OVER (ORDER BY a1 ASC) AS RankY,
NTILE(4) OVER (ORDER BY a1 ASC) AS TileZ,
*
FROM A
ORDER BY a1 ASC;
```
**SQL 代码 2** (创建临时表并使用IDENTITY函数):
```sql
CREATE TABLE tmp_table1 (ID INT IDENTITY(1, 1), A1 INT, A2 INT, A3 INT, A4 INT);
INSERT INTO tmp_table1 (A1, A2, A3, A4)
SELECT *
FROM A;
SELECT *
FROM tmp_table1;
```
这些示例展示了如何在实际应用中使用SQL解决复杂的问题，涵盖了删除重复记录、多表查询、窗口函数等多种技术。通过这些示例的学习，可以提高面试者对于SQL的理解和运用能力，为面试做更充分的准备。
