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mongodb: operators and projections

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Marcello 2022-09-03 15:10:39 +02:00
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commit d38a98c370
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47
docs/database/mongo-db.md
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@ -36,13 +36,13 @@ db.createCollection(name, {options}) # explicit collection creation
db.<collection>.insertOne({document}) # implicit collection creation
```
## Operators
## Operators (MQL Syntax)
```json
/* --- Update operators --- */
{ "$inc": { "<key>": <increment>, ... } } // Increment value
{ "$inc": { "<key>": "<increment>", ... } } // Increment value
{ "$set": { "<key>": "<value>", ... } } // Set value
{ "$push": { "<key>": "<value>", ... } } // add a value to an array field
{ "$push": { "<key>": "<value>", ... } } // add a value to an array field or turn field into array
/* --- Query Operators --- */
{ "<key>": { "$in": [ "<value_1>", "<value_2>", ...] } } // Membership
@ -58,20 +58,30 @@ db.<collection>.insertOne({document}) # implicit collection creation
{ "<key>": { "$ne": "<value>" }} // !=
/* --- Logic Operators (DEFAULT $and) --- */
{ "$and": [ { <statement> }, ...] }
{ "$or": [ { <statement> }, ...] }
{ "$nor": [ { <statement> }, ...] }
{ "$not": { <statement> } }
{ "$and": [ { "<expression>" }, ...] }
{ "$or": [ { "<expression>" }, ...] }
{ "$nor": [ { "<expression>" }, ...] }
{ "$not": { "<expression>" } }
/* --- Array Operators --- */
{ "<key>": { "$all": ["value>", "<value>", ...] } } // field contains all values
{ "<key>": { "$size": "<value>" } }
{ "<array-key>": { "$elemMatch": { "<item-key>": "<expression>" } } } // elements in array must match an expression
/* --- REGEX Operator --- */
{ "<key>": { "$regex": "/pattern/", "$options": "<options>" } }
{ "<key>": { "$regex": "pattern", "$options": "<options>" } }
{ "<key>": { "$regex": "/pattern/<options>" } }
{ "<key>": "/pattern/<options>" }
```
### Expressive Query Operator
`$<key>` is used to access the value of the field dynamically
> **Note**: `$<key>` is used to access the value of the field dynamically
```json
{ "$expr": { <expression> } } // aggregation expression, variables, conditional expressions
{ "$expr": { "$comparison_operator": [ "$<key>", "$<key>" ] } } // compare field values
{ "$expr": { "<expression>" } } // aggregation expression, variables, conditional expressions
{ "$expr": { "$<comparison_operator>": [ "$<key>", "$<key>" ] } } // compare field values (operators use aggregation syntax)
```
## CRUD Operations
@ -121,13 +131,20 @@ db.<collection>.insertMany([ { document }, { document } ] , { "ordered": false }
```sh
db.<collection>.findOne() # find only one document
db.<collection>.find(filter) # show selected documents
db.<collection>.find(filter, {"<key>": 1}) # show selected values form documents (1 or true => show, 0 or false => don't show, cant mix 0 and 1)
db.<collection>.find(filter, {_id: 0, "<key>": 1}) # only _id can be set to 0 with other keys at 1
db.<collection>.find().pretty() # show documents formatted
db.<collection>.find().limit(n) # show n documents
db.<collection>.find().limit(n).skip(k) # show n documents skipping k docs
db.<collection>.find().count() # number of found docs
db.<collection>.find().sort({key1: 1, ... , key_n: -1}) # show documents sorted by specified keys in ascending (1) or descending (-1) order
db.<collection>.find().sort({ "<key-1>": 1, ... , "<key-n>": -1 }) # show documents sorted by specified keys in ascending (1) or descending (-1) order
# projection
db.<collection>.find(filter, { "<key>": 1 }) # show selected values form documents (1 or true => show, 0 or false => don't show, cant mix 0 and 1)
db.<collection>.find(filter, { _id: 0, "<key>": 1 }) # only _id can be set to 0 with other keys at 1
db.<collection>.find(filter, { "<array-key>": { "$elemMatch": { "<item-key>": "<expression>" } } }) # project only elements matching the expression
# sub documents & arrays
db.<collection>.find({ "<key>.<sub-key>.<sub-key>": "<expression>" })
db.<collection>.find({ "<array-key>.<index>.<sub-key>": "<expression>" })
# GeoJSON - https://docs.mongodb.com/manual/reference/operator/query/near/index.html
db.<collection>.find(
@ -149,6 +166,8 @@ db.<collection>.find().hint( { $natural : 1 } ) # force the query to perform a
db.<collection>.find().hint( { $natural : -1 } ) # force the query to perform a reverse collection scan
```
> **Note**: `{ <key>: <value> }` in case of a field array will match if the array _contains_ the value
### Update
[Update Operators](https://docs.mongodb.com/manual/reference/operator/update/ "Update Operators Documentation")