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search:
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# Class: Constraints 


_Validation constraints attached to a field._



<div data-search-exclude markdown="1">



URI: [fts:Constraints](https://specs.frictionlessdata.io/table-schema/Constraints)





```mermaid
 classDiagram
    class Constraints
    click Constraints href "../Constraints/"
      Constraints : enum
        
      Constraints : maximum
        
      Constraints : maxLength
        
      Constraints : minimum
        
      Constraints : minLength
        
      Constraints : pattern
        
      Constraints : required
        
      Constraints : unique
        
      
```




<!-- no inheritance hierarchy -->

## Slots

| Name | Cardinality and Range | Description | Inheritance |
| ---  | --- | --- | --- |
| [required](required.md) | 0..1 <br/> [Boolean](Boolean.md) | Whether the field must have a value in every row | direct |
| [unique](unique.md) | 0..1 <br/> [Boolean](Boolean.md) | Whether each value of this field must be distinct across rows | direct |
| [pattern](pattern.md) | 0..1 <br/> [String](String.md) | Regular expression that all values must match (XML Schema regex syntax) | direct |
| [enum](enum.md) | * <br/> [String](String.md) | Closed list of allowed values | direct |
| [minLength](minLength.md) | 0..1 <br/> [Integer](Integer.md) | Minimum length for string values (or item count for arrays) | direct |
| [maxLength](maxLength.md) | 0..1 <br/> [Integer](Integer.md) | Maximum length for string values (or item count for arrays) | direct |
| [minimum](minimum.md) | 0..1 <br/> [String](String.md) | Minimum permissible value for numeric, date, datetime, time, year, and yearmo... | direct |
| [maximum](maximum.md) | 0..1 <br/> [String](String.md) | Maximum permissible value (matches `minimum` semantics) | direct |





## Usages

| used by | used in | type | used |
| ---  | --- | --- | --- |
| [Field](Field.md) | [constraints](constraints.md) | range | [Constraints](Constraints.md) |












## Identifier and Mapping Information





### Schema Source


* from schema: https://specs.frictionlessdata.io/table-schema




## Mappings

| Mapping Type | Mapped Value |
| ---  | ---  |
| self | fts:Constraints |
| native | fts:Constraints |






## LinkML Source

<!-- TODO: investigate https://stackoverflow.com/questions/37606292/how-to-create-tabbed-code-blocks-in-mkdocs-or-sphinx -->

### Direct

<details>
```yaml
name: Constraints
description: Validation constraints attached to a field.
from_schema: https://specs.frictionlessdata.io/table-schema
attributes:
  required:
    name: required
    description: Whether the field must have a value in every row. An empty string
      is considered missing per Frictionless conventions.
    from_schema: https://specs.frictionlessdata.io/table-schema
    rank: 1000
    domain_of:
    - Constraints
    range: boolean
  unique:
    name: unique
    description: Whether each value of this field must be distinct across rows.
    from_schema: https://specs.frictionlessdata.io/table-schema
    rank: 1000
    domain_of:
    - Constraints
    range: boolean
  pattern:
    name: pattern
    description: Regular expression that all values must match (XML Schema regex syntax).
    from_schema: https://specs.frictionlessdata.io/table-schema
    rank: 1000
    domain_of:
    - Constraints
    range: string
  enum:
    name: enum
    description: Closed list of allowed values. Treated as an enumeration in target
      schemas that distinguish that case.
    from_schema: https://specs.frictionlessdata.io/table-schema
    rank: 1000
    domain_of:
    - Constraints
    range: string
    multivalued: true
  minLength:
    name: minLength
    description: Minimum length for string values (or item count for arrays).
    from_schema: https://specs.frictionlessdata.io/table-schema
    rank: 1000
    domain_of:
    - Constraints
    range: integer
  maxLength:
    name: maxLength
    description: Maximum length for string values (or item count for arrays).
    from_schema: https://specs.frictionlessdata.io/table-schema
    rank: 1000
    domain_of:
    - Constraints
    range: integer
  minimum:
    name: minimum
    description: Minimum permissible value for numeric, date, datetime, time, year,
      and yearmonth types. The literal type matches the field's type.
    from_schema: https://specs.frictionlessdata.io/table-schema
    rank: 1000
    domain_of:
    - Constraints
    range: string
  maximum:
    name: maximum
    description: Maximum permissible value (matches `minimum` semantics).
    from_schema: https://specs.frictionlessdata.io/table-schema
    rank: 1000
    domain_of:
    - Constraints
    range: string

```
</details>

### Induced

<details>
```yaml
name: Constraints
description: Validation constraints attached to a field.
from_schema: https://specs.frictionlessdata.io/table-schema
attributes:
  required:
    name: required
    description: Whether the field must have a value in every row. An empty string
      is considered missing per Frictionless conventions.
    from_schema: https://specs.frictionlessdata.io/table-schema
    rank: 1000
    owner: Constraints
    domain_of:
    - Constraints
    range: boolean
  unique:
    name: unique
    description: Whether each value of this field must be distinct across rows.
    from_schema: https://specs.frictionlessdata.io/table-schema
    rank: 1000
    owner: Constraints
    domain_of:
    - Constraints
    range: boolean
  pattern:
    name: pattern
    description: Regular expression that all values must match (XML Schema regex syntax).
    from_schema: https://specs.frictionlessdata.io/table-schema
    rank: 1000
    owner: Constraints
    domain_of:
    - Constraints
    range: string
  enum:
    name: enum
    description: Closed list of allowed values. Treated as an enumeration in target
      schemas that distinguish that case.
    from_schema: https://specs.frictionlessdata.io/table-schema
    rank: 1000
    owner: Constraints
    domain_of:
    - Constraints
    range: string
    multivalued: true
  minLength:
    name: minLength
    description: Minimum length for string values (or item count for arrays).
    from_schema: https://specs.frictionlessdata.io/table-schema
    rank: 1000
    owner: Constraints
    domain_of:
    - Constraints
    range: integer
  maxLength:
    name: maxLength
    description: Maximum length for string values (or item count for arrays).
    from_schema: https://specs.frictionlessdata.io/table-schema
    rank: 1000
    owner: Constraints
    domain_of:
    - Constraints
    range: integer
  minimum:
    name: minimum
    description: Minimum permissible value for numeric, date, datetime, time, year,
      and yearmonth types. The literal type matches the field's type.
    from_schema: https://specs.frictionlessdata.io/table-schema
    rank: 1000
    owner: Constraints
    domain_of:
    - Constraints
    range: string
  maximum:
    name: maximum
    description: Maximum permissible value (matches `minimum` semantics).
    from_schema: https://specs.frictionlessdata.io/table-schema
    rank: 1000
    owner: Constraints
    domain_of:
    - Constraints
    range: string

```
</details></div>