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CritasWang merged 2 commits into from
Apr 1, 2025
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add full outer join and cross join to table model #679

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5c5126b
add full outer join and cross join to table model
leto-b Mar 31, 2025
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add full outer join and cross join to table model
leto-b Mar 31, 2025
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108 changes: 104 additions & 4 deletions src/UserGuide/Master/Table/SQL-Manual/From-Join-Clause.md
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Original file line number Diff line number Diff line change
Expand Up @@ -70,10 +70,9 @@ The `JOIN` clause combines two tables based on specific conditions, typically pr

In the current version of IoTDB, the following joins are supported:

1. **Inner Join**: Combines rows that meet the join condition, effectively returning the intersection of the two tables.
2. **Full Outer Join**: Returns all records from both tables, inserting `NULL` values for unmatched rows.

**Note:** The join condition in IoTDB must be an equality condition on the `time` column. This restriction ensures that rows are joined based on the equality of their timestamps.
1. **Inner Join**: Combines rows that meet the join condition, effectively returning the intersection of the two tables. The join condition must be an equality condition on the `time` column.
2. **Full Outer Join**: Returns all records from both tables, inserting `NULL` values for unmatched rows. The join condition can be any equality expression.
3. **Cross Join**: Represents the Cartesian product of two tables.

### 3.1 Inner Join

Expand Down Expand Up @@ -120,6 +119,19 @@ An **outer join** returns rows even when no matching records exist in the other

IoTDB currently supports only `FULL [OUTER] JOIN`. This type returns all records from both tables. If a record in one table has no match in the other, `NULL` values are returned for the unmatched fields. `FULL JOIN` **must use explicit join conditions**.

```sql
//Specify the join condition after the ON keyword or specify the join columns after the USING keyword.
SELECT selectExpr [, selectExpr] ... FROM <TABLE_NAME> FULL [OUTER] JOIN <TABLE_NAME> joinCriteria [WHERE whereCondition]

joinCriteria
: ON booleanExpression
| USING '(' identifier (',' identifier)* ')'
;
```

### 3.3 Cross Join
A cross join represents the Cartesian product of two tables, returning all possible combinations of the N rows from the left table and the M rows from the right table, resulting in N*M rows. This type of join is the least commonly used in practice.

## 4. Example Queries

The [Example Data page](../Reference/Sample-Data.md)page provides SQL statements to construct table schemas and insert data. By downloading and executing these statements in the IoTDB CLI, you can import the data into IoTDB. This data can be used to test and run the example SQL queries included in this documentation, allowing you to reproduce the described results.
Expand Down Expand Up @@ -399,4 +411,92 @@ Query Results:
+-----------------------------+-------+------------+-------+------------+
Total line number = 21
It costs 0.073s
```

Example 3: The join condition is based on a non-time column.

```sql
SELECT
region,
t1.time as time1,
t1.temperature as temperature1,
t2.time as time2,
t2.temperature as temperature2
FROM
table1 t1 FULL JOIN table2 t2
USING(region)
LIMIT 10
```

Query Results:

```sql
+------+-----------------------------+------------+-----------------------------+------------+
|region| time1|temperature1| time2|temperature2|
+------+-----------------------------+------------+-----------------------------+------------+
| 上海|2024-11-29T11:00:00.000+08:00| null|2024-11-29T11:00:00.000+08:00| null|
| 上海|2024-11-29T11:00:00.000+08:00| null|2024-11-28T08:00:00.000+08:00| 85.0|
| 上海|2024-11-29T11:00:00.000+08:00| null|2024-11-30T00:00:00.000+08:00| 90.0|
| 上海|2024-11-29T11:00:00.000+08:00| null|2024-11-29T00:00:00.000+08:00| 85.0|
| 上海|2024-11-30T09:30:00.000+08:00| 90.0|2024-11-29T11:00:00.000+08:00| null|
| 上海|2024-11-30T09:30:00.000+08:00| 90.0|2024-11-28T08:00:00.000+08:00| 85.0|
| 上海|2024-11-30T09:30:00.000+08:00| 90.0|2024-11-30T00:00:00.000+08:00| 90.0|
| 上海|2024-11-30T09:30:00.000+08:00| 90.0|2024-11-29T00:00:00.000+08:00| 85.0|
| 上海|2024-11-29T18:30:00.000+08:00| 90.0|2024-11-29T11:00:00.000+08:00| null|
| 上海|2024-11-29T18:30:00.000+08:00| 90.0|2024-11-28T08:00:00.000+08:00| 85.0|
+------+-----------------------------+------------+-----------------------------+------------+
Total line number = 10
It costs 0.040s
```

#### 4.2.3 Cross Join

**Example 1: Explicit Join**

```sql
SELECT table1.*, table2.* FROM table1 CROSS JOIN table2 LIMIT 8;
```

Query Results:

```sql
+-----------------------------+------+--------+---------+--------+-----------+-----------+--------+------+-----------------------------+-----------------------------+------+--------+---------+--------+-----------+-----------+--------+------+-----------------------------+
| time|region|plant_id|device_id|model_id|maintenance|temperature|humidity|status| arrival_time| time|region|plant_id|device_id|model_id|maintenance|temperature|humidity|status| arrival_time|
+-----------------------------+------+--------+---------+--------+-----------+-----------+--------+------+-----------------------------+-----------------------------+------+--------+---------+--------+-----------+-----------+--------+------+-----------------------------+
|2024-11-30T09:30:00.000+08:00| 上海| 3002| 101| F| 360| 90.0| 35.2| true| null|2024-11-30T00:00:00.000+08:00| 上海| 3002| 101| F| 360| 90.0| 35.2| true| null|
|2024-11-30T09:30:00.000+08:00| 上海| 3002| 101| F| 360| 90.0| 35.2| true| null|2024-11-29T00:00:00.000+08:00| 上海| 3001| 101| D| 360| 85.0| 35.1| null|2024-11-29T10:00:13.000+08:00|
|2024-11-30T09:30:00.000+08:00| 上海| 3002| 101| F| 360| 90.0| 35.2| true| null|2024-11-27T00:00:00.000+08:00| 北京| 1001| 101| B| 180| 85.0| 35.1| true|2024-11-27T16:37:01.000+08:00|
|2024-11-30T09:30:00.000+08:00| 上海| 3002| 101| F| 360| 90.0| 35.2| true| null|2024-11-29T11:00:00.000+08:00| 上海| 3002| 100| E| 180| null| 45.1| true| null|
|2024-11-30T09:30:00.000+08:00| 上海| 3002| 101| F| 360| 90.0| 35.2| true| null|2024-11-28T08:00:00.000+08:00| 上海| 3001| 100| C| 90| 85.0| 35.2| false|2024-11-28T08:00:09.000+08:00|
|2024-11-30T09:30:00.000+08:00| 上海| 3002| 101| F| 360| 90.0| 35.2| true| null|2024-11-26T13:37:00.000+08:00| 北京| 1001| 100| A| 180| 90.0| 35.1| true|2024-11-26T13:37:34.000+08:00|
|2024-11-30T14:30:00.000+08:00| 上海| 3002| 101| F| 360| 90.0| 34.8| true|2024-11-30T14:30:17.000+08:00|2024-11-30T00:00:00.000+08:00| 上海| 3002| 101| F| 360| 90.0| 35.2| true| null|
|2024-11-30T14:30:00.000+08:00| 上海| 3002| 101| F| 360| 90.0| 34.8| true|2024-11-30T14:30:17.000+08:00|2024-11-29T00:00:00.000+08:00| 上海| 3001| 101| D| 360| 85.0| 35.1| null|2024-11-29T10:00:13.000+08:00|
+-----------------------------+------+--------+---------+--------+-----------+-----------+--------+------+-----------------------------+-----------------------------+------+--------+---------+--------+-----------+-----------+--------+------+-----------------------------+
Total line number = 8
It costs 0.282s
```

**Example 2: Implicit Join**

```sql
SELECT table1.*, table2.* FROM table1, table2 LIMIT 8;
```

Query Results:

```sql
+-----------------------------+------+--------+---------+--------+-----------+-----------+--------+------+-----------------------------+-----------------------------+------+--------+---------+--------+-----------+-----------+--------+------+-----------------------------+
| time|region|plant_id|device_id|model_id|maintenance|temperature|humidity|status| arrival_time| time|region|plant_id|device_id|model_id|maintenance|temperature|humidity|status| arrival_time|
+-----------------------------+------+--------+---------+--------+-----------+-----------+--------+------+-----------------------------+-----------------------------+------+--------+---------+--------+-----------+-----------+--------+------+-----------------------------+
|2024-11-30T09:30:00.000+08:00| 上海| 3002| 101| F| 360| 90.0| 35.2| true| null|2024-11-30T00:00:00.000+08:00| 上海| 3002| 101| F| 360| 90.0| 35.2| true| null|
|2024-11-30T09:30:00.000+08:00| 上海| 3002| 101| F| 360| 90.0| 35.2| true| null|2024-11-29T00:00:00.000+08:00| 上海| 3001| 101| D| 360| 85.0| 35.1| null|2024-11-29T10:00:13.000+08:00|
|2024-11-30T09:30:00.000+08:00| 上海| 3002| 101| F| 360| 90.0| 35.2| true| null|2024-11-27T00:00:00.000+08:00| 北京| 1001| 101| B| 180| 85.0| 35.1| true|2024-11-27T16:37:01.000+08:00|
|2024-11-30T09:30:00.000+08:00| 上海| 3002| 101| F| 360| 90.0| 35.2| true| null|2024-11-29T11:00:00.000+08:00| 上海| 3002| 100| E| 180| null| 45.1| true| null|
|2024-11-30T09:30:00.000+08:00| 上海| 3002| 101| F| 360| 90.0| 35.2| true| null|2024-11-28T08:00:00.000+08:00| 上海| 3001| 100| C| 90| 85.0| 35.2| false|2024-11-28T08:00:09.000+08:00|
|2024-11-30T09:30:00.000+08:00| 上海| 3002| 101| F| 360| 90.0| 35.2| true| null|2024-11-26T13:37:00.000+08:00| 北京| 1001| 100| A| 180| 90.0| 35.1| true|2024-11-26T13:37:34.000+08:00|
|2024-11-30T14:30:00.000+08:00| 上海| 3002| 101| F| 360| 90.0| 34.8| true|2024-11-30T14:30:17.000+08:00|2024-11-30T00:00:00.000+08:00| 上海| 3002| 101| F| 360| 90.0| 35.2| true| null|
|2024-11-30T14:30:00.000+08:00| 上海| 3002| 101| F| 360| 90.0| 34.8| true|2024-11-30T14:30:17.000+08:00|2024-11-29T00:00:00.000+08:00| 上海| 3001| 101| D| 360| 85.0| 35.1| null|2024-11-29T10:00:13.000+08:00|
+-----------------------------+------+--------+---------+--------+-----------+-----------+--------+------+-----------------------------+-----------------------------+------+--------+---------+--------+-----------+-----------+--------+------+-----------------------------+
Total line number = 8
It costs 0.047s
```
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