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Update INSERT/CREATE syntax in nGQL.md (#371)
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* Update INSERT syntax in nGQL.md

* address darion's comments

* Change Define to Create

* Fix some layout problems
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@dangleptr
dangleptr authored May 14, 2019
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60 changes: 30 additions & 30 deletions docs/nGQL.md
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# Nebula Graph Query Language (nGQL)

## About nGQL
`NGQL` is a declarative, textual query language like SQL, but for graphs. Unlike SQL, nGQL is all about expressing graph patterns. NGQL is a work in progress. We will add more features and further simplify the existing ones.
`nGQL` is a declarative, textual query language like SQL, but for graphs. Unlike SQL, nGQL is all about expressing graph patterns. nGQL is a work in progress. We will add more features and further simplify the existing ones. There might be inconsistency between the syntax specs and implementation for the time being.
## Goals
- Easy to learn
- Easy to understand
Expand Down Expand Up @@ -98,7 +98,7 @@
#### Choose a graph space
Nebula supports multiple graph spaces. Data in different graph spaces are physically isolated. Before executing a query, a graph space needs to be selected using the following statement

<span style="color:blue">**USE **</span> <graphspace_name>
<span style="color:blue">**USE**</span> <graphspace_name>

#### Return a data set
Simply return a single value or a data set
Expand All @@ -107,22 +107,22 @@ Simply return a single value or a data set

<return\_value\_decl> ::= **vid** | <vid\_list> | <tuple\_list\_decl> | <var\>

#### Define a tag
#### Create a tag
The following statement defines a **new** tag

<span style="color:blue">**DEFINE TAG**</span> <tag\_name> (<prop\_def\_list>)
<span style="color:blue">**CREATE TAG**</span> <tag\_name> (<prop\_def\_list>)

<tag\_name> ::= <label\>
<prop\_def\_list> ::= <prop\_def>+
<prop\_def> ::= <prop\_name> <type\>
<prop\_name> ::= <label\>
<tag\_name> ::= <label\> <br>
<prop\_def\_list> ::= <prop\_def>+ <br>
<prop\_def> ::= <prop\_name>,<type\> <br>
<prop\_name> ::= <label\> <br>

#### Modify a tag type

#### Define an edge type
#### Create an edge type
The following statement defines a **new** edge type

<span style="color:blue">**DEFINE EDGE**</span> <edge\_type\_name> (<prop\_def\_list>)
<span style="color:blue">**CREATE EDGE**</span> <edge\_type\_name> (<prop\_def\_list>)

<edge\_type\_name> := <label\>

Expand All @@ -131,13 +131,13 @@ The following statement defines a **new** edge type
#### Insert vertices
The following statement inserts one or more vertices

<span style="color:blue">**INSERT VERTEX**</span> [<span style="color:blue">**NO OVERWRITE**</span>] "("<br/>
<span style="indent:20">[ <vertex\_id> [ <span style="color:blue">**WITH**</span> <tag\_name> [(<prop\_list>)] <span style="color:blue">**VALUES**</span> (<prop\_value\_list>) ]+ ]+</span><br/>
")"
<span style="color:blue">**INSERT VERTEX**</span> [<span style="color:blue">**NO OVERWRITE**</span>] <tag\_list> <span style="color:blue">**VALUES**</span> <vertex\_list> <br/>

<vertex\_id> ::= **vid**
<prop\_list> ::= <prop\_name> (, <prop\_name>)+
<prop\_value\_list> ::= **VALUE** (, **VALUE**)*
<tag\_list> ::= <tag\_name>(<prop\_list>) (, <tag\_name>(<prop\_list>))\* <br/>
<vertex\_list> ::= <vertex\_id>:(<prop\_value\_list>) (, <vertex\_id>:(<prop\_value\_list>))\* <br/>
<vertex\_id> ::= **vid** <br/>
<prop\_list> ::= <prop\_name> (, <prop\_name>)\* <br/>
<prop\_value\_list> ::= **VALUE** (, **VALUE**)\* <br/>

#### Insert edges

Expand All @@ -155,9 +155,9 @@ The following statement updates a vertex
[<span style="color:blue">**WHERE**</span> <conditions\>]
[<span style="color:blue">**YIELD**</span> <field\_list>]

<update\_decl> ::= <update\_form1> | <update\_form2>
<update\_form1> ::= <prop\_name> = <expression\> {,<prop\_name> = <expression\>}+
<update\_form2> ::= (<prop\_list>) = (<value\_list>) | (<prop\_list>) = <var\>
<update\_decl> ::= <update\_form1> | <update\_form2> <br>
<update\_form1> ::= <prop\_name> = <expression\> {,<prop\_name> = <expression\>}+ <br>
<update\_form2> ::= (<prop\_list>) = (<value\_list>) | (<prop\_list>) = <var\> <br>

#### Update an edge
The following statement updates an edge
Expand All @@ -177,17 +177,17 @@ Navigate from given vertices to their neighbors according to the given condition
[<span style="color:blue">**WHERE**</span> <filter\_list>]
[<span style="color:blue">**YIELD**</span> <field\_list>]

<steps\_decl> ::= **integer** | **integer** <span style="color:blue">**TO**</span> **integer** | <span style="color:blue">**UPTO**</span> **interger**
<steps\_decl> ::= **integer** | **integer** <span style="color:blue">**TO**</span> **integer** | <span style="color:blue">**UPTO**</span> **interger** <br>
<data\_set\_decl> ::= [data\_set] [[<span style="color:blue">**AS**</span>] <label\>]<br/>
<data\_set> ::= **vid** | <vid\_list> | <tuple\_list\_decl> | <var\><br/>
<edge\_type\_decl> ::= <edge\_type\_list> [<span style="color:blue">**AS**</span> <label\>]
<edge\_type\_list> ::= <edge\_type> {, <edge\_type>}\*
<edge\_type> ::= <label\>
<edge\_type\_list> ::= <edge\_type> {, <edge\_type>}\* <br>
<edge\_type> ::= <label\> <br>

<filter\_list> ::= <filter\> {<span style="color:blue">**AND**</span> | <span style="color:blue">**OR**</span> <filter\>}\*
<filter\> ::= <expression\> <span style="color:blue">**>**</span> | <span style="color:blue">**>=**</span> | <span style="color:blue">**<**</span> | <span style="color:blue">**<=**</span> | <span style="color:blue">**==**</span> | <span style="color:blue">**!=**</span> <expression\> | <expression\> <span style="color:blue">**IN**</span> <value\_list\>
<field\_list> ::= <return\_field> {, <return\_field>}\*
<return\_field> ::= <expression\> [<span style="color:blue">**AS**</span> <label\>]
<filter\_list> ::= <filter\> {<span style="color:blue">**AND**</span> | <span style="color:blue">**OR**</span> <filter\>}\* <br>
<filter\> ::= <expression\> <span style="color:blue">**>**</span> | <span style="color:blue">**>=**</span> | <span style="color:blue">**<**</span> | <span style="color:blue">**<=**</span> | <span style="color:blue">**==**</span> | <span style="color:blue">**!=**</span> <expression\> | <expression\> <span style="color:blue">**IN**</span> <value\_list\> <br>
<field\_list> ::= <return\_field> {, <return\_field>}\* <br>
<return\_field> ::= <expression\> [<span style="color:blue">**AS**</span> <label\>] <br>

<span style="color:blue">**WHERE**</span> clause only applies to the results that are going to be returned. It will not be applied to the intermediate results (See the detail description of the <span style="color:blue">**STEP[S]**</span> clause)

Expand Down Expand Up @@ -240,10 +240,10 @@ The following statement does a pattern match, and can return tuple list or paths
### Property Reference
It's common to refer a property in the statement, such as in <span style="color:blue">**WHERE**</span> clause and <span style="color:blue">**YIELD**</span> clause. In nGQL, the reference to a property is defined as

<property_ref> ::= <object\> "." <prop\_name>
<object\> ::= <alias\_name> | <alias\_with\_tag> | <var\>
<alias\_name> ::= <label\>
<alias\_wiht\_tag> ::= <alias\_name> '[' <tag\_name> "]"
<property_ref> ::= <object\> "." <prop\_name> <br>
<object\> ::= <alias\_name> | <alias\_with\_tag> | <var\> <br>
<alias\_name> ::= <label\> <br>
<alias\_wiht\_tag> ::= <alias\_name> '[' <tag\_name> "]" <br>

<var\> always starts with "$". There are two special variables: $_ and $$.

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