docs/UserGuide/Syntax-Conventions/NodeName-In-Path.md

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# Node Name in Path

Node name is a special identifier, it can also be wildcard `*` and `**`. When creating timeseries, node name can not be wildcard. In query statment, you can use wildcard to match one or more nodes of path.

## Wildcard

`*` represents one node. For example, `root.vehicle.*.sensor1` represents a 4-node path which is prefixed with `root.vehicle` and suffixed with `sensor1`.

`**` represents (`*`)+, which is one or more nodes of `*`. For example, `root.vehicle.device1.**` represents all paths prefixed by `root.vehicle.device1` with nodes num greater than or equal to 4, like `root.vehicle.device1.*`, `root.vehicle.device1.*.*`, `root.vehicle.device1.*.*.*`, etc; `root.vehicle.**.sensor1` represents a path which is prefixed with `root.vehicle` and suffixed with `sensor1` and has at least 4 nodes.

As `*` can also be used in expressions of select clause to represent multiplication, below are examples to help you better understand the usage of `* `:

```sql
# create timeseries root.sg.`a*b`
create timeseries root.sg.`a*b` with datatype=FLOAT,encoding=PLAIN;

# As described in Identifier part, a*b should be quoted.
# "create timeseries root.sg.a*b with datatype=FLOAT,encoding=PLAIN" is wrong. 

# create timeseries root.sg.a
create timeseries root.sg.a with datatype=FLOAT,encoding=PLAIN;

# create timeseries root.sg.b
create timeseries root.sg.b with datatype=FLOAT,encoding=PLAIN;

# query data of root.sg.`a*b`
select `a*b` from root.sg
# Header of result dataset
|Time|root.sg.a*b|

# multiplication of root.sg.a and root.sg.b
select a*b from root.sg
# Header of result dataset
|Time|root.sg.a * root.sg.b|
```

## Identifier

When node name is not wildcard, it is a identifier, which means the constraints on it is the same as described in Identifier part.

- Create timeseries statement:

```sql
# Node name contains special characters like ` and .,all nodes of this timeseries are: ["root","sg","www.`baidu.com"]
create timeseries root.sg.`www.``baidu.com`.a with datatype=FLOAT,encoding=PLAIN;

# Node name is a real number.
create timeseries root.sg.`111`.a with datatype=FLOAT,encoding=PLAIN;
```

After executing above statments, execute "show timeseries"，below is the result：

```sql
+---------------------------+-----+-------------+--------+--------+-----------+----+----------+
|                 timeseries|alias|database|dataType|encoding|compression|tags|attributes|
+---------------------------+-----+-------------+--------+--------+-----------+----+----------+
|            root.sg.`111`.a| null|      root.sg|   FLOAT|   PLAIN|     SNAPPY|null|      null|
|root.sg.`www.``baidu.com`.a| null|      root.sg|   FLOAT|   PLAIN|     SNAPPY|null|      null|
+---------------------------+-----+-------------+--------+--------+-----------+----+----------+
```

- Insert statment:

```sql
# Node name contains special characters like . and `
insert into root.sg.`www.``baidu.com`(timestamp, a) values(1, 2);

# Node name is a real number.
insert into root.sg(timestamp, `111`) values (1, 2);
```

- Query statement:

```sql
# Node name contains special characters like . and `
select a from root.sg.`www.``baidu.com`;

# Node name is a real number.
select `111` from root.sg
```

Results:

```sql
# select a from root.sg.`www.``baidu.com`
+-----------------------------+---------------------------+
|                         Time|root.sg.`www.``baidu.com`.a|
+-----------------------------+---------------------------+
|1970-01-01T08:00:00.001+08:00|                        2.0|
+-----------------------------+---------------------------+

# select `111` from root.sg
+-----------------------------+-----------+
|                         Time|root.sg.111|
+-----------------------------+-----------+
|1970-01-01T08:00:00.001+08:00|        2.0|
+-----------------------------+-----------+
```