4.2.3.8. DM
4.2.3.8.1. 分区表查询
CREATE TABLE unisql_partition (
unisql_id NUMBER,
unisql_name VARCHAR2(50),
unisql_salary NUMBER(10,2),
unisql_hire_date DATE,
CONSTRAINT unisql_partition_pk PRIMARY KEY (unisql_id, unisql_hire_date)
)
PARTITION BY RANGE (unisql_hire_date) (
PARTITION unisql_partition_p1 VALUES LESS THAN (TO_DATE('2024-01-01', 'YYYY-MM-DD')),
PARTITION unisql_partition_p2 VALUES LESS THAN (TO_DATE('2025-01-01', 'YYYY-MM-DD'))
);
INSERT INTO unisql_partition (unisql_id,unisql_name,unisql_salary, unisql_hire_date)values (1, 'John', 5000, TO_DATE('2023-01-01','YYYY-MM-DD'));
INSERT INTO unisql_partition (unisql_id,unisql_name,unisql_salary, unisql_hire_date)values (2, 'Mary', 6000, TO_DATE( '2023-02-15','YYYY-MM-DD'));
INSERT INTO unisql_partition (unisql_id,unisql_name,unisql_salary, unisql_hire_date)values (3, 'Tom', 7000, TO_DATE( '2023-03-20','YYYY-MM-DD'));
INSERT INTO unisql_partition (unisql_id,unisql_name,unisql_salary, unisql_hire_date)values (4, 'Alice', 8000, TO_DATE('2023-04-10','YYYY-MM-DD'));
INSERT INTO unisql_partition (unisql_id,unisql_name,unisql_salary, unisql_hire_date)values (5, 'Bob', 9000, TO_DATE('2023-05-01','YYYY-MM-DD'));
-- 转换前Oracle SQL：
SELECT unisql_id,unisql_name,unisql_salary, unisql_hire_date FROM unisql_partition PARTITION (unisql_partition_p1);
UNISQL_ID|UNISQL_NAME|UNISQL_SALARY|UNISQL_HIRE_DATE |
---------+-----------+-------------+-----------------------+
1|John | 5000|2023-01-01 00:00:00.000|
2|Mary | 6000|2023-02-15 00:00:00.000|
3|Tom | 7000|2023-03-20 00:00:00.000|
4|Alice | 8000|2023-04-10 00:00:00.000|
5|Bob | 9000|2023-05-01 00:00:00.000|
-- 转换后达梦 SQL：
SELECT unisql_id,unisql_name,unisql_salary, unisql_hire_date FROM unisql_partition PARTITION (unisql_partition_p1)
unisql_id|unisql_name|unisql_salary|unisql_hire_date |
unisql_id|unisql_name|unisql_salary|unisql_hire_date|
---------+-----------+-------------+----------------+
1|John | 5000.00| 2023-01-01|
2|Mary | 6000.00| 2023-02-15|
3|Tom | 7000.00| 2023-03-20|
4|Alice | 8000.00| 2023-04-10|
5|Bob | 9000.00| 2023-05-01|
4.2.3.8.2. pivot行转列
CREATE TABLE unisql_pivot(id int ,name varchar(64),score NUMBER ,subject varchar2(64));
INSERT INTO unisql_pivot VALUES(1,'张三',70,'CHINESE');
INSERT INTO unisql_pivot VALUES(1,'张三',90,'MATH');
INSERT INTO unisql_pivot VALUES(1,'张三',95,'ENGLISH');
INSERT INTO unisql_pivot VALUES(2,'李四',75,'CHINESE');
INSERT INTO unisql_pivot VALUES(2,'李四',85,'MATH');
INSERT INTO unisql_pivot VALUES(2,'李四',90,'ENGLISH');
INSERT INTO unisql_pivot VALUES(3,'王五',90,'CHINESE');
INSERT INTO unisql_pivot VALUES(3,'王五',90,'MATH');
INSERT INTO unisql_pivot VALUES(3,'王五',90,'ENGLISH');
-- 转换前Oracle SQL：
SELECT id,name,chinese_score,match_score,english_score
FROM unisql_pivot
pivot(
min(score) FOR subject IN('CHINESE' AS chinese_score,'MATH' AS match_score,'ENGLISH' AS english_score)
)
WHERE id IN (1, 2, 3) ORDER BY id;
ID|NAME|CHINESE_SCORE|MATCH_SCORE|ENGLISH_SCORE|
--+----+-------------+-----------+-------------+
1|张三 | 70| 90| 95|
2|李四 | 75| 85| 90|
3|王五 | 90| 90| 90|
-- 转换后达梦 SQL：
SELECT id,name,chinese_score,match_score,english_score
FROM unisql_pivot
pivot(
min(score) FOR subject IN('CHINESE' AS chinese_score,'MATH' AS match_score,'ENGLISH' AS english_score)
)
WHERE id IN (1, 2, 3) ORDER BY id
id|name|chinese_score|match_score|english_score|
--+----+-------------+-----------+-------------+
1|张三 | 70| 90| 95|
2|李四 | 75| 85| 90|
3|王五 | 90| 90| 90|
4.2.3.8.3. unpivot列转行
-- 建表语句
CREATE TABLE unisql_unpivot(id INT,name VARCHAR(64),chinese NUMBER,math INT,english INT);
INSERT INTO unisql_unpivot VALUES(1,'张三',70,90,95);
INSERT INTO unisql_unpivot VALUES(2,'李四',75,85,90);
INSERT INTO unisql_unpivot VALUES(3,'张三',90,90,90);
-- 转换前Oracle SQL:
SELECT
id,
name,
score ,
subject
FROM
unisql_unpivot UNPIVOT(score FOR subject IN(chinese, math, english))
WHERE
id IN (1, 2, 3) ORDER BY id;
ID|NAME|SCORE|SUBJECT|
--+----+-----+-------+
1|张三 | 70|CHINESE|
1|张三 | 90|MATH |
1|张三 | 95|ENGLISH|
2|李四 | 75|CHINESE|
2|李四 | 85|MATH |
2|李四 | 90|ENGLISH|
3|张三 | 90|CHINESE|
3|张三 | 90|MATH |
3|张三 | 90|ENGLISH|
-- 转换后达梦 SQL:
SELECT
id,
name,
score ,
subject
FROM
unisql_unpivot UNPIVOT(score FOR subject IN(chinese, math, english))
WHERE
id IN (1, 2, 3) ORDER BY id
id|name|score|subject|
--+----+-----+-------+
1|张三 | 90|math |
1|张三 | 70|chinese|
1|张三 | 95|english|
2|李四 | 85|math |
2|李四 | 90|english|
2|李四 | 75|chinese|
3|张三 | 90|math |
3|张三 | 90|chinese|
3|张三 | 90|english|
4.2.3.8.4. MINUS 差集
{ (< SQL- 查询语句 1>) }
MINUS
{ (< SQL- 查询语句 2>) }
-- 转换前Oracle SQL:
SELECT * FROM unisql_collect_1
MINUS
SELECT * FROM unisql_collect_2;
ID|NAME|CHINESE|MATH|ENGLISH|
--+----+-------+----+-------+
3|王五 | 90| 90| 90|
4|秦六 | 65| 65| 60|
-- 转换后达梦 SQL:
SELECT * FROM unisql_collect_1
MINUS
SELECT * FROM unisql_collect_2
id|name|chinese|math|english|
--+----+-------+----+-------+
3|王五 | 90| 90| 90|
4|秦六 | 65| 65| 60|
4.2.3.8.5. AS作为别名
通常AS在数据库中作为保留关键字，一般不建议作为字段的别名，但是有时候开发人员在编写SQL语句时，存在使用AS作为别名的情况。 统一SQL支持AS作为别名时到目标库的转换。
示例
-- 转换前Oracle SQL:
SELECT 0 as, 1 as,2 "as", 3 a, 4 as b, count(*) as FROM dual;
0AS|1AS|as|A|B|COUNT(*)AS|
---+---+--+-+-+----------+
0| 1| 2|3|4| 1|
-- 转换后达梦 SQL:
SELECT 0 AS "as",1 AS "as",2 AS "as",3 AS a,4 AS b,count(1) AS "as" FROM dual
as|as|as|a|b|as|
--+--+--+-+-+--+
0| 1| 2|3|4| 1|