Update values.md: more clear

Author: BohuTANG

docs/en/sql-reference/10-sql-commands/20-query-syntax/values.md

@@ -5,24 +5,28 @@ import FunctionDescription from '@site/src/components/FunctionDescription';
 
 <FunctionDescription description="Introduced or updated: v1.2.65"/>
 
-The VALUES clause is used to define a set of rows explicitly for use in queries. It allows you to provide a list of values that can be used as a temporary table in your SQL statements.
+The VALUES clause creates an inline table by explicitly defining rows of data. This temporary table can be used directly or within other SQL statements.
 
 ## Syntax
 
 ```sql
-VALUES (value_1_1, value_1_2, ...), (value_2_1, value_2_2, ...), ...
+SELECT ...
+FROM ( VALUES ( <expr> [ , <expr> [ , ... ] ] ) [ , ( ... ) ] ) [ [ AS ] <table_alias> [ ( <column_alias> [, ... ] ) ] ]
+[ ... ]
 ```
-- The VALUES clause is followed by sets of values enclosed in parentheses.
-- Each set of values represents a row to be inserted into the temporary table.
-- Within each set of values, the individual values are comma-separated and correspond to the columns of the temporary table.
-- Databend automatically assigns default column names like *col0*, *col1*, *col2*, and so on when you insert multiple rows without specifying column names.
+
+**Key Points:**
+- The VALUES clause must be enclosed in parentheses when used in a FROM clause: `FROM (VALUES ...)`
+- Each parenthesized group of expressions represents one row
+- Column names are automatically assigned as **col0**, **col1**, etc. (zero-based indexing)
+- You can provide custom column names using table aliases
 
 ## Examples
 
-These examples demonstrate using the VALUES clause to show city data in various formats: directly, or ordered by population:
+### Basic Usage
 
 ```sql
--- Directly return data
+-- Direct usage with automatic column names (col0, col1)
 VALUES ('Toronto', 2731571), ('Vancouver', 631486), ('Montreal', 1704694);
 
 col0     |col1   |
@@ -31,7 +35,7 @@ Toronto  |2731571|
 Vancouver| 631486|
 Montreal |1704694|
 
--- Order data
+-- With ORDER BY
 VALUES ('Toronto', 2731571), ('Vancouver', 631486), ('Montreal', 1704694) ORDER BY col1;
 
 col0     |col1   |
@@ -41,56 +45,36 @@ Montreal |1704694|
 Toronto  |2731571|
 ```
 
-These examples demonstrate how the VALUES clause can be used in a SELECT statement:
+### In SELECT Statements
 
 ```sql
--- Select a single column
-SELECT col1 
+-- Select specific column - note the parentheses around VALUES
+SELECT col1
 FROM (VALUES ('Toronto', 2731571), ('Vancouver', 631486), ('Montreal', 1704694));
 
-col1   |
--------+
-2731571|
- 631486|
-1704694|
-
--- Select columns with aliases
+-- Custom column names - VALUES must be enclosed in parentheses
 SELECT * FROM (
-    VALUES ('Toronto', 2731571), 
-           ('Vancouver', 631486), 
+    VALUES ('Toronto', 2731571),
+           ('Vancouver', 631486),
            ('Montreal', 1704694)
 ) AS CityPopulation(City, Population);
 
-city     |population|
----------+----------+
-Toronto  |   2731571|
-Vancouver|    631486|
-Montreal |   1704694|
-
--- Select columns with aliases and sorting
+-- With column aliases and sorting
 SELECT col0 AS City, col1 AS Population
 FROM (VALUES ('Toronto', 2731571), ('Vancouver', 631486), ('Montreal', 1704694))
 ORDER BY col1 DESC
 LIMIT 1;
-
-city   |population|
--------+----------+
-Toronto|   2731571|
 ```
 
-This example demonstrates how to use the VALUES clause to create a temporary table within a Common Table Expression (CTE):
+### With Common Table Expressions (CTE)
 
 ```sql
 WITH citypopulation(city, population) AS (
     VALUES ('Toronto', 2731571),
            ('Vancouver', 631486),
            ('Montreal', 1704694)
 )
-SELECT citypopulation.city, citypopulation.population FROM citypopulation;
-
-city     |population|
----------+----------+
-Toronto  |   2731571|
-Vancouver|    631486|
-Montreal |   1704694|
-```
+SELECT city, population FROM citypopulation;
+```
+
+> **Important**: When using VALUES in a FROM clause or CTE, it must be enclosed in parentheses: `FROM (VALUES ...)` or `AS (VALUES ...)`. This is required syntax.