add set operations in table from 2091

src/.vuepress/sidebar/V2.0.x/en-Table.ts

@@ -233,6 +233,7 @@ export const enSidebar = {
             { text: 'ORDER BY Clause', link: 'OrderBy-Clause' },
             { text: 'LIMIT&OFFSET Clause', link: 'Limit-Offset-Clause' },
             { text: 'Nested Queries', link: 'Nested-Queries' },
+            { text: 'Set Operations', link: 'Set-Operations_apache' },
           ],
         },
         { text: 'Maintenance Statements', link: 'SQL-Maintenance-Statements_apache' },

src/.vuepress/sidebar/V2.0.x/zh-Table.ts

@@ -230,6 +230,7 @@ export const zhSidebar = {
             { text: 'ORDER BY子句', link: 'OrderBy-Clause' },
             { text: 'LIMIT&OFFSET子句', link: 'Limit-Offset-Clause' },
             { text: '嵌套查询', link: 'Nested-Queries' },
+            { text: '集合操作', link: 'Set-Operations_apache' },
           ],
         },
         { text: '运维语句', link: 'SQL-Maintenance-Statements_apache' },

src/.vuepress/sidebar_timecho/V2.0.x/en-Table.ts

@@ -265,6 +265,7 @@ export const enSidebar = {
             { text: 'LIMIT&OFFSET Clause', link: 'Limit-Offset-Clause' },
             { text: 'Nested Queries', link: 'Nested-Queries' },
             { text: 'Pattern Query', link: 'Row-Pattern-Recognition_timecho' },
+            { text: 'Set Operations', link: 'Set-Operations_timecho' },
           ],
         },
         { text: 'Maintenance Statements', link: 'SQL-Maintenance-Statements_timecho' },

src/.vuepress/sidebar_timecho/V2.0.x/zh-Table.ts

@@ -256,6 +256,7 @@ export const zhSidebar = {
             { text: 'LIMIT&OFFSET子句', link: 'Limit-Offset-Clause' },
             { text: '嵌套查询', link: 'Nested-Queries' },
             { text: '模式查询', link: 'Row-Pattern-Recognition_timecho' },
+            { text: '集合操作', link: 'Set-Operations_timecho' },
           ],
         },
         { text: '运维语句', link: 'SQL-Maintenance-Statements_timecho' },

src/UserGuide/Master/Table/SQL-Manual/Set-Operations_apache.md

@@ -0,0 +1,295 @@
+<!--
+
+    Licensed to the Apache Software Foundation (ASF) under one
+    or more contributor license agreements.  See the NOTICE file
+    distributed with this work for additional information
+    regarding copyright ownership.  The ASF licenses this file
+    to you under the Apache License, Version 2.0 (the
+    "License"); you may not use this file except in compliance
+    with the License.  You may obtain a copy of the License at
+
+        http://www.apache.org/licenses/LICENSE-2.0
+
+    Unless required by applicable law or agreed to in writing,
+    software distributed under the License is distributed on an
+    "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+    KIND, either express or implied.  See the License for the
+    specific language governing permissions and limitations
+    under the License.
+
+-->
+# Set Operations
+
+IoTDB natively supports standard SQL set operations, including three core operators: **UNION**, **INTERSECT**, and **EXCEPT**. These operations enable seamless merging, comparison, and filtering of query results from multiple time-series data sources, greatly improving the flexibility and efficiency of time-series data analysis.
+
+> Note: This feature is available since version 2.0.9-beta.
+
+## 1. UNION
+### 1.1 Overview
+The UNION operator combines all rows from two result sets (order not guaranteed), supporting both duplicate elimination (default) and duplicate retention modes.
+
+### 1.2 Syntax
+```sql
+query UNION (ALL | DISTINCT) query
+```
+
+**Description**
+1. **Duplicate Handling**
+    - Default (`UNION` or `UNION DISTINCT`): Automatically removes duplicate rows.
+    - `UNION ALL`: Preserves all rows (including duplicates) with higher performance.
+
+2. **Input Requirements**
+    - The two queries must return the same number of columns.
+    - Corresponding columns must have compatible data types:
+        - Numeric compatibility: `INT32`, `INT64`, `FLOAT`, and `DOUBLE` are fully compatible with each other.
+        - String compatibility: `TEXT` and `STRING` are fully compatible.
+        - Special rule: `INT64` is compatible with `TIMESTAMP`.
+
+3. **Result Set Rules**
+    - Column names and order are inherited from the first query.
+
+### 1.3 Examples
+Using the [sample data](../Reference/Sample-Data.md):
+
+1. Get distinct non-null device and temperature records from `table1` and `table2`
+```sql
+SELECT device_id, temperature FROM table1 WHERE temperature IS NOT NULL
+UNION
+SELECT device_id, temperature FROM table2 WHERE temperature IS NOT NULL;
+
+-- Equivalent to:
+SELECT device_id, temperature FROM table1 WHERE temperature IS NOT NULL
+UNION DISTINCT
+SELECT device_id, temperature FROM table2 WHERE temperature IS NOT NULL;
+```
+
+Result:
+```
++---------+-----------+
+|device_id|temperature|
++---------+-----------+
+|      101|       90.0|
+|      101|       85.0|
+|      100|       90.0|
+|      100|       85.0|
+|      100|       88.0|
++---------+-----------+
+Total line number = 5
+It costs 0.074s
+```
+
+2. Get all non-null device and temperature records from `table1` and `table2` (including duplicates)
+```sql
+SELECT device_id, temperature FROM table1 WHERE temperature IS NOT NULL
+UNION ALL
+SELECT device_id, temperature FROM table2 WHERE temperature IS NOT NULL;
+```
+
+Result:
+```
++---------+-----------+
+|device_id|temperature|
++---------+-----------+
+|      101|       90.0|
+|      101|       90.0|
+|      101|       85.0|
+|      101|       85.0|
+|      101|       85.0|
+|      101|       85.0|
+|      100|       90.0|
+|      100|       85.0|
+|      100|       85.0|
+|      100|       88.0|
+|      100|       90.0|
+|      100|       90.0|
+|      101|       90.0|
+|      101|       85.0|
+|      101|       85.0|
+|      100|       85.0|
+|      100|       90.0|
++---------+-----------+
+Total line number = 17
+It costs 0.108s
+```
+
+> **Notes**
+> - Set operations **do not guarantee result order**; actual output may differ from examples.
+
+
+## 2. INTERSECT
+### 2.1 Overview
+The INTERSECT operator returns rows that exist in both result sets (order not guaranteed), supporting both duplicate elimination (default) and duplicate retention modes.
+
+### 2.2 Syntax
+```sql
+query1 INTERSECT [ALL | DISTINCT] query2
+```
+
+**Description**
+1. **Duplicate Handling**
+    - Default (`INTERSECT` or `INTERSECT DISTINCT`): Automatically removes duplicate rows.
+    - `INTERSECT ALL`: Preserves duplicate rows, with slightly lower performance.
+
+2. **Precedence Rules**
+    - `INTERSECT` has higher precedence than `UNION` and `EXCEPT`
+      (e.g., `A UNION B INTERSECT C` is equivalent to `A UNION (B INTERSECT C)`).
+    - Evaluation is left-to-right
+      (e.g., `A INTERSECT B INTERSECT C` is equivalent to `(A INTERSECT B) INTERSECT C`).
+
+3. **Input Requirements**
+    - The two queries must return the same number of columns.
+    - Corresponding columns must have compatible data types (same rules as UNION).
+    - NULL values are treated as equal (`NULL IS NOT DISTINCT FROM NULL`).
+    - If the `time` column is not included in `SELECT`, it does not participate in comparison and will not appear in the result.
+
+4. **Result Set Rules**
+    - Column names and order are inherited from the first query.
+
+### 2.3 Examples
+Using the [sample data](../Reference/Sample-Data.md):
+
+1. Get distinct common device and temperature records from `table1` and `table2`
+```sql
+SELECT device_id, temperature FROM table1
+INTERSECT
+SELECT device_id, temperature FROM table2;
+
+-- Equivalent to:
+SELECT device_id, temperature FROM table1
+INTERSECT DISTINCT
+SELECT device_id, temperature FROM table2;
+```
+
+Result:
+```
++---------+-----------+
+|device_id|temperature|
++---------+-----------+
+|      101|       90.0|
+|      101|       85.0|
+|      100|       null|
+|      100|       90.0|
+|      100|       85.0|
++---------+-----------+
+Total line number = 5
+It costs 0.087s
+```
+
+2. Get all common device and temperature records from `table1` and `table2` (including duplicates)
+```sql
+SELECT device_id, temperature FROM table1
+INTERSECT ALL
+SELECT device_id, temperature FROM table2;
+```
+
+Result:
+```
++---------+-----------+
+|device_id|temperature|
++---------+-----------+
+|      100|       85.0|
+|      100|       90.0|
+|      100|       null|
+|      101|       85.0|
+|      101|       85.0|
+|      101|       90.0|
++---------+-----------+
+Total line number = 6
+It costs 0.139s
+```
+
+> **Notes**
+> - Set operations **do not guarantee result order**.
+> - When mixed with `UNION`/`EXCEPT`, use parentheses to explicitly specify precedence
+    >   (e.g., `A INTERSECT (B UNION C)`).
+
+
+## 3. EXCEPT
+### 3.1 Overview
+The EXCEPT operator returns rows that exist in the first result set but **not** in the second (order not guaranteed), supporting both duplicate elimination (default) and duplicate retention modes.
+
+### 3.2 Syntax
+```sql
+query1 EXCEPT [ALL | DISTINCT] query2
+```
+
+**Description**
+1. **Duplicate Handling**
+    - Default (`EXCEPT` or `EXCEPT DISTINCT`): Automatically removes duplicate rows.
+    - `EXCEPT ALL`: Preserves duplicate rows, with slightly lower performance.
+
+2. **Precedence Rules**
+    - `EXCEPT` has the same precedence as `UNION`, and lower precedence than `INTERSECT`
+      (e.g., `A INTERSECT B EXCEPT C` is equivalent to `(A INTERSECT B) EXCEPT C`).
+    - Evaluation is left-to-right
+      (e.g., `A EXCEPT B EXCEPT C` is equivalent to `(A EXCEPT B) EXCEPT C`).
+
+3. **Input Requirements**
+    - The two queries must return the same number of columns.
+    - Corresponding columns must have compatible data types (same rules as UNION).
+    - NULL values are treated as equal (`NULL IS NOT DISTINCT FROM NULL`).
+    - If the `time` column is not included in `SELECT`, it does not participate in comparison and will not appear in the result.
+
+4. **Result Set Rules**
+    - Column names and order are inherited from the first query.
+
+### 3.3 Examples
+Using the [sample data](../Reference/Sample-Data.md):
+
+1. Get distinct records from `table1` that do not exist in `table2`
+```sql
+SELECT device_id, temperature FROM table1
+EXCEPT
+SELECT device_id, temperature FROM table2;
+
+-- Equivalent to:
+SELECT device_id, temperature FROM table1
+EXCEPT DISTINCT
+SELECT device_id, temperature FROM table2;
+```
+
+Result:
+```
++---------+-----------+
+|device_id|temperature|
++---------+-----------+
+|      101|       null|
+|      100|       88.0|
++---------+-----------+
+Total line number = 2
+It costs 0.173s
+```
+
+2. Get all records from `table1` that do not exist in `table2` (including duplicates)
+```sql
+SELECT device_id, temperature FROM table1
+EXCEPT ALL
+SELECT device_id, temperature FROM table2;
+```
+
+Result:
+```
++---------+-----------+
+|device_id|temperature|
++---------+-----------+
+|      100|       85.0|
+|      100|       88.0|
+|      100|       90.0|
+|      100|       90.0|
+|      100|       null|
+|      101|       85.0|
+|      101|       85.0|
+|      101|       90.0|
+|      101|       null|
+|      101|       null|
+|      101|       null|
+|      101|       null|
++---------+-----------+
+Total line number = 12
+It costs 0.155s
+```
+
+> **Notes**
+> - Set operations **do not guarantee result order**.
+> - When mixed with `UNION`/`INTERSECT`, use parentheses to explicitly specify precedence
+    >   (e.g., `A EXCEPT (B INTERSECT C)`).