mirror of https://gitee.com/bigwinds/arangodb
34 lines
1.1 KiB
Plaintext
34 lines
1.1 KiB
Plaintext
Functions
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=========
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AQL supports functions to allow more complex computations. Functions can be
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called at any query position where an expression is allowed. The general
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function call syntax is:
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```js
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FUNCTIONNAME(arguments)
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```
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where *FUNCTIONNAME* is the name of the function to be called, and *arguments*
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is a comma-separated list of function arguments. If a function does not need any
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arguments, the argument list can be left empty. However, even if the argument
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list is empty the parentheses around it are still mandatory to make function
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calls distinguishable from variable names.
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Some example function calls:
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```js
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HAS(user, "name")
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LENGTH(friends)
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COLLECTIONS()
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```
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In contrast to collection and variable names, function names are case-insensitive,
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i.e. *LENGTH(foo)* and *length(foo)* are equivalent.
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### Extending AQL
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It is possible to extend AQL with user-defined functions. These functions need to
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be written in JavaScript, and have to be registered before they can be used in a query.
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Please refer to [Extending AQL](../Extending/index.html) for more details.
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