<!--

    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.

-->

# Metadata Operations

## 1. Database Management

### 1.1 Create Database

**Syntax:**

```SQL
CREATE DATABASE (IF NOT EXISTS)? <DATABASE_NAME> (WITH properties)?
```

[Detailed syntax reference](../Basic-Concept/Database-Management_timecho.md#_1-1-create-a-database)

**Examples:**

```SQL
CREATE DATABASE database1;
CREATE DATABASE IF NOT EXISTS database1;

-- Create database with 1-year TTL;
CREATE DATABASE IF NOT EXISTS database1 with(TTL=31536000000);
```

### 1.2 Use Database

**Syntax:**

```SQL
USE <DATABASE_NAME>
```

**Examples:**

```SQL
USE database1;
```

### 1.3 View Current Database

**Syntax:**

```SQL
SHOW CURRENT_DATABASE;
```

**Examples:**

```SQL
SHOW CURRENT_DATABASE;
```
```shell
+---------------+
|CurrentDatabase|
+---------------+
|           null|
+---------------+
```
```sql
USE database1;
SHOW CURRENT_DATABASE;
```
```shell
+---------------+
|CurrentDatabase|
+---------------+
|      database1|
+---------------+
```

### 1.4 List All Databases

**Syntax:**

```SQL
SHOW DATABASES (DETAILS)?
```

[Detailed syntax reference](../Basic-Concept/Database-Management_timecho.md#_1-4-view-all-databases)

**Examples:**

```SQL
show databases;
```
```shell
+------------------+-------+-----------------------+---------------------+---------------------+
|          Database|TTL(ms)|SchemaReplicationFactor|DataReplicationFactor|TimePartitionInterval|
+------------------+-------+-----------------------+---------------------+---------------------+
|         database1|    INF|                      1|                    1|            604800000|
|information_schema|    INF|                   null|                 null|                 null|
+------------------+-------+-----------------------+---------------------+---------------------+
```
```sql
show databases details;
```
```shell
+------------------+-------+-----------------------+---------------------+---------------------+--------------------+------------------+
|          Database|TTL(ms)|SchemaReplicationFactor|DataReplicationFactor|TimePartitionInterval|SchemaRegionGroupNum|DataRegionGroupNum|
+------------------+-------+-----------------------+---------------------+---------------------+--------------------+------------------+
|         database1|    INF|                      1|                    1|            604800000|                   1|                 2|
|information_schema|    INF|                   null|                 null|                 null|                null|              null|
+------------------+-------+-----------------------+---------------------+---------------------+--------------------+------------------+
```

### 1.5 Modify Database

**Syntax:**

```SQL
ALTER DATABASE (IF EXISTS)? database=identifier SET PROPERTIES propertyAssignments
```

**Examples:**

```SQL
ALTER DATABASE database1 SET PROPERTIES TTL=31536000000;
```

### 1.6 Drop Database

**Syntax:**

```SQL
DROP DATABASE (IF EXISTS)? <DATABASE_NAME>
```

**Examples:**

```SQL
DROP DATABASE IF EXISTS database1;
```

## 2. Table Management

### 2.1 Create Table

**Syntax:**

```SQL
createTableStatement
    : CREATE TABLE (IF NOT EXISTS)? qualifiedName
        '(' (columnDefinition (',' columnDefinition)*)? ')'
        charsetDesc?
        comment?
        (WITH properties)?
     ;

charsetDesc
    : DEFAULT? (CHAR SET | CHARSET | CHARACTER SET) EQ? identifierOrString
    ;

columnDefinition
    : identifier columnCategory=(TAG | ATTRIBUTE | TIME) charsetName? comment?
    | identifier type (columnCategory=(TAG | ATTRIBUTE | TIME | FIELD))? charsetName? comment?
    ;

charsetName
    : CHAR SET identifier
    | CHARSET identifier
    | CHARACTER SET identifier
    ;

comment
    : COMMENT string
    ;
```

[Detailed syntax reference](../Basic-Concept/Table-Management_timecho.md#_1-1-create-a-table)

**Examples:**

```SQL
CREATE TABLE table1 (
  time TIMESTAMP TIME,
  region STRING TAG,
  plant_id STRING TAG,
  device_id STRING TAG,
  model_id STRING ATTRIBUTE,
  maintenance STRING ATTRIBUTE COMMENT 'maintenance',
  temperature FLOAT FIELD COMMENT 'temperature',
  humidity FLOAT FIELD COMMENT 'humidity',
  status BOOLEAN FIELD COMMENT 'status',
  arrival_time TIMESTAMP FIELD COMMENT 'arrival_time'
) COMMENT 'table1' WITH (TTL=31536000000);

CREATE TABLE if not exists tableB ();

CREATE TABLE tableC (
  "Site" STRING TAG,
  "Temperature" int32 FIELD COMMENT 'temperature'
 ) with (TTL=DEFAULT);
 
 -- Custom time column: named time_test, located in the second column of the table. (Support from V2.0.8.2)
 CREATE TABLE table1 (
     region STRING TAG, 
     time_user_defined TIMESTAMP TIME, 
     temperature FLOAT FIELD
 );
```

Note: If your terminal does not support multi-line paste (e.g., Windows CMD), please reformat the SQL statement into a single line before execution.


### 2.2 List Tables

**Syntax:**

```SQL
SHOW TABLES (DETAILS)? ((FROM | IN) database_name)?
```

**Examples:**

```SQL
show tables from database1;
```
```shell
+---------+---------------+
|TableName|        TTL(ms)|
+---------+---------------+
|   table1|    31536000000|
+---------+---------------+
```
```sql
show tables details from database1;
```
```shell
+---------------+-----------+------+-------+
|      TableName|    TTL(ms)|Status|Comment|
+---------------+-----------+------+-------+
|         table1|31536000000| USING| table1|
+---------------+-----------+------+-------+
```

### 2.3 Describe Table Columns

**Syntax:**

```SQL
(DESC | DESCRIBE) <TABLE_NAME> (DETAILS)?
```

**Examples:**

```SQL
desc table1;
```
```shell
+------------+---------+---------+
|  ColumnName| DataType| Category|
+------------+---------+---------+
|        time|TIMESTAMP|     TIME|
|      region|   STRING|      TAG|
|    plant_id|   STRING|      TAG|
|   device_id|   STRING|      TAG|
|    model_id|   STRING|ATTRIBUTE|
| maintenance|   STRING|ATTRIBUTE|
| temperature|    FLOAT|    FIELD|
|    humidity|    FLOAT|    FIELD|
|      status|  BOOLEAN|    FIELD|
|arrival_time|TIMESTAMP|    FIELD|
+------------+---------+---------+
```
```sql
desc table1 details;
```
```shell
+------------+---------+---------+------+------------+
|  ColumnName| DataType| Category|Status|     Comment|
+------------+---------+---------+------+------------+
|        time|TIMESTAMP|     TIME| USING|        null|
|      region|   STRING|      TAG| USING|        null|
|    plant_id|   STRING|      TAG| USING|        null|
|   device_id|   STRING|      TAG| USING|        null|
|    model_id|   STRING|ATTRIBUTE| USING|        null|
| maintenance|   STRING|ATTRIBUTE| USING| maintenance|
| temperature|    FLOAT|    FIELD| USING| temperature|
|    humidity|    FLOAT|    FIELD| USING|    humidity|
|      status|  BOOLEAN|    FIELD| USING|      status|
|arrival_time|TIMESTAMP|    FIELD| USING|arrival_time|
+------------+---------+---------+------+------------+
```


### 2.4 View Table Creation Statement

**Syntax:**

```SQL
SHOW CREATE TABLE <TABLE_NAME>
```

**Examples:**

```SQL
show create table table1;
```
```shell
+------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table|                                                                                                                                                                                                                                                                     Create Table|
+------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
|table1|CREATE TABLE "table1" ("region" STRING TAG,"plant_id" STRING TAG,"device_id" STRING TAG,"model_id" STRING ATTRIBUTE,"maintenance" STRING ATTRIBUTE,"temperature" FLOAT FIELD,"humidity" FLOAT FIELD,"status" BOOLEAN FIELD,"arrival_time" TIMESTAMP FIELD) WITH (ttl=31536000000)|
+------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
Total line number = 1
```


### 2.5 Modify Table

**Syntax:**

```SQL
#addColumn;
ALTER TABLE (IF EXISTS)? tableName=qualifiedName ADD COLUMN (IF NOT EXISTS)? column=columnDefinition COMMENT 'column_comment';               
#dropColumn;
| ALTER TABLE (IF EXISTS)? tableName=qualifiedName DROP COLUMN (IF EXISTS)? column=identifier;                    
#setTableProperties;
// set TTL can use this;
| ALTER TABLE (IF EXISTS)? tableName=qualifiedName SET PROPERTIES propertyAssignments;                
| COMMENT ON TABLE tableName=qualifiedName IS 'table_comment';
| COMMENT ON COLUMN tableName.column IS 'column_comment';
#changeColumndatatype;
| ALTER TABLE (IF EXISTS)? tableName=qualifiedName ALTER COLUMN (IF EXISTS)? column=identifier SET DATA TYPE new_type=type;
```

**Examples:**

```SQL
ALTER TABLE table1 ADD COLUMN IF NOT EXISTS a TAG COMMENT 'a';
ALTER TABLE table1 ADD COLUMN IF NOT EXISTS b FLOAT FIELD COMMENT 'b';
ALTER TABLE table1 set properties TTL=3600;
COMMENT ON TABLE table1 IS 'table1';
COMMENT ON COLUMN table1.a IS null;
ALTER TABLE table1 ALTER COLUMN IF EXISTS b SET DATA TYPE DOUBLE;
```

### 2.6 Drop Table

**Syntax:**

```SQL
DROP TABLE (IF EXISTS)? <TABLE_NAME>
```

**Examples:**

```SQL
DROP TABLE table1;
DROP TABLE database1.table1;
```