JoinType (Starlink-UK API)

java.lang.Object
- uk.ac.starlink.table.join.JoinType

```
public abstract class JoinType
extends Object
```
Defines how a set of matched rows from input tables (RowLink objects) are used to select rows for inclusion in an output table which represents the result of the matching operation. This corresponds to the type of the join in database terminology, though the naming of the instances of this class do not follow that terminology (left outer join etc), and the options here present a more complete set.
Instances of this class are available as public static members of it. Currently, these instances should only be used with the results of pair matches (ones involving exactly two tables).

Since:

5 Sep 2005

Author:

Mark Taylor

Field Summary

Fields
Modifier and Type	Field and Description
`static JoinType`	`_1AND2` Selects only rows with input from both input tables.
`static JoinType`	`_1NOT2` Selects only rows in the first input table which are not matched by any row in the second input table.
`static JoinType`	`_1OR2` Selects rows with input from either or both input tables.
`static JoinType`	`_1XOR2` Selects only rows with input from exactly one of the two input tables.
`static JoinType`	`_2NOT1` Selects only rows in the second input table which are not matched by any row in the first input table.
`static JoinType`	`_ALL1` Selects all output rows with input from the first input table.
`static JoinType`	`_ALL2` Selects all output rows with input from the second input table.

Method Summary

All Methods Static Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method and Description
`abstract String`	`getDescription()` Returns a short textual description of this type.
`String`	`getName()` Returns the name of this type.
`static JoinType[]`	`getPairTypes()` Returns a list of all the known types which apply to two-table matches.
`abstract boolean`	`getUsedMatchFlag()` Returns a value which indicates whether the matchScore is ever non-empty in the output table.
`abstract boolean[]`	`getUsedTableFlags()` Returns an array of flags indicating whether each of the tables in the input will ever have non-empty rows in the output.
`abstract LinkSet`	`processLinks(LinkSet links, int[] rowCounts)` Turns a set of links which represent matches from the matching operation into a set of links which represent the rows to output.
`String`	`toString()` Returns the name of this type.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Field Detail
  - _1AND2
```
public static final JoinType _1AND2
```
    Selects only rows with input from both input tables.
  - _1OR2
```
public static final JoinType _1OR2
```
    Selects rows with input from either or both input tables.
  - _ALL1
```
public static final JoinType _ALL1
```
    Selects all output rows with input from the first input table.
  - _ALL2
```
public static final JoinType _ALL2
```
    Selects all output rows with input from the second input table.
  - _2NOT1
```
public static final JoinType _2NOT1
```
    Selects only rows in the second input table which are not matched by any row in the first input table.
  - _1NOT2
```
public static final JoinType _1NOT2
```
    Selects only rows in the first input table which are not matched by any row in the second input table.
  - _1XOR2
```
public static final JoinType _1XOR2
```
    Selects only rows with input from exactly one of the two input tables.
- Method Detail
  - processLinks
```
public abstract LinkSet processLinks(LinkSet links,
                                     int[] rowCounts)
```
    Turns a set of links which represent matches from the matching operation into a set of links which represent the rows to output. links is a set of RowLink objects; if the matching operation was between two tables, each element will represent a pair match (have two RowRefs, with table indices of 0 and 1 respectively). The ordering of links may influence the order of the returned collection. links may be modified by this method, and the returned value may or may not be the same object as the input links itself.
    
    Parameters:
    
    links - set of RowLinks representing actual matches
    
    rowCounts - numbers of rows in the tables on which the match was performed
    
    Returns:
    
    set of RowLinks representing rows for the output table
  - getUsedTableFlags
```
public abstract boolean[] getUsedTableFlags()
```
    Returns an array of flags indicating whether each of the tables in the input will ever have non-empty rows in the output.
    
    Returns:
    
    2-element boolean array indicating whether first and second input tables appear in output
  - getUsedMatchFlag
```
public abstract boolean getUsedMatchFlag()
```
    Returns a value which indicates whether the matchScore is ever non-empty in the output table.
    
    Returns:
    
    true iff the matchScore may be used in the output
  - getName
```
public String getName()
```
    Returns the name of this type.
    
    Returns:
    
    name
  - getDescription
```
public abstract String getDescription()
```
    Returns a short textual description of this type.
    
    Returns:
    
    description
  - toString
```
public String toString()
```
    Returns the name of this type.
    
    Overrides:
    
    toString in class Object
  - getPairTypes
```
public static JoinType[] getPairTypes()
```
    Returns a list of all the known types which apply to two-table matches.
    
    Returns:
    
    array of the 7 known types

Class JoinType

Field Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

_1AND2

_1OR2

_ALL1

_ALL2

_2NOT1

_1NOT2

_1XOR2

Method Detail

processLinks

getUsedTableFlags

getUsedMatchFlag

getName

getDescription

toString

getPairTypes