Comparison

java.lang.Object
- org.h2.expression.Expression
- - org.h2.expression.Comparison

```
public class Comparison
extends Expression
```
Example comparison expressions are ID=1, NAME=NAME, NAME IS NULL.

Field Summary

Fields
Modifier and Type	Field and Description
`static int`	`BIGGER` The comparison type meaning > as in ID>1.
`static int`	`BIGGER_EQUAL` The comparison type meaning >= as in ID>=1.
`static int`	`EQUAL` The comparison type meaning = as in ID=1.
`static int`	`EQUAL_NULL_SAFE` The comparison type meaning ID IS 1 (ID IS NOT DISTINCT FROM 1).
`static int`	`FALSE` This is a pseudo comparison type that is only used for index conditions.
`static int`	`IN_LIST` This is a pseudo comparison type that is only used for index conditions.
`static int`	`IN_QUERY` This is a pseudo comparison type that is only used for index conditions.
`static int`	`IS_NOT_NULL` The comparison type meaning IS NOT NULL as in NAME IS NOT NULL.
`static int`	`IS_NULL` The comparison type meaning IS NULL as in NAME IS NULL.
`static int`	`NOT_EQUAL` The comparison type meaning <> as in ID<>1.
`static int`	`NOT_EQUAL_NULL_SAFE` The comparison type meaning ID IS NOT 1 (ID IS DISTINCT FROM 1).
`static int`	`NULL_SAFE` This is a flag meaning the comparison is null safe (meaning never returns NULL even if one operand is NULL).
`static int`	`SMALLER` The comparison type meaning < as in ID<1.
`static int`	`SMALLER_EQUAL` The comparison type meaning <= as in ID<=1.
`static int`	`SPATIAL_INTERSECTS` This is a comparison type that is only used for spatial index conditions (operator "&&").

Constructor Summary

Constructors
Constructor and Description

Comparison(Session session, int compareType, Expression left, Expression right)

Constructors
Constructor and Description
`Comparison(Session session, int compareType, Expression left, Expression right)`

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`addFilterConditions(TableFilter filter, boolean outerJoin)` Add conditions to a table filter if they can be evaluated.
`void`	`createIndexConditions(Session session, TableFilter filter)` Create index conditions if possible and attach them to the table filter.
`int`	`getCost()` Estimate the cost to process the expression.
`int`	`getDisplaySize()` Get the display size of this expression.
`Expression`	`getExpression(boolean getLeft)` Get the left or the right sub-expression of this condition.
`Expression`	`getNotIfPossible(Session session)` If it is possible, return the negated expression.
`long`	`getPrecision()` Get the precision of this expression.
`int`	`getScale()` Get the scale of this expression.
`java.lang.String`	`getSQL()` Get the SQL statement of this expression.
`int`	`getType()` Return the data type.
`Value`	`getValue(Session session)` Return the resulting value for the current row.
`boolean`	`isEverything(ExpressionVisitor visitor)` Check if this expression and all sub-expressions can fulfill a criteria.
`void`	`mapColumns(ColumnResolver resolver, int level)` Map the columns of the resolver to expression columns.
`Expression`	`optimize(Session session)` Try to optimize the expression.
`void`	`setEvaluatable(TableFilter tableFilter, boolean b)` Tell the expression columns whether the table filter can return values now.
`void`	`updateAggregate(Session session)` Update an aggregate value.

Methods inherited from class org.h2.expression.Expression
getAlias, getBooleanValue, getColumnName, getExpressionColumns, getExpressionColumns, getNonAliasExpression, getNullable, getSchemaName, getTableAlias, getTableName, isAutoIncrement, isConstant, isValueSet, isWildcard, toString

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

- Field Detail
  - NULL_SAFE
```
public static final int NULL_SAFE
```
    This is a flag meaning the comparison is null safe (meaning never returns NULL even if one operand is NULL). Only EQUAL and NOT_EQUAL are supported currently.
    
    See Also:
    
    Constant Field Values
  - EQUAL
```
public static final int EQUAL
```
    The comparison type meaning = as in ID=1.
    
    See Also:
    
    Constant Field Values
  - EQUAL_NULL_SAFE
```
public static final int EQUAL_NULL_SAFE
```
    The comparison type meaning ID IS 1 (ID IS NOT DISTINCT FROM 1).
    
    See Also:
    
    Constant Field Values
  - BIGGER_EQUAL
```
public static final int BIGGER_EQUAL
```
    The comparison type meaning >= as in ID>=1.
    
    See Also:
    
    Constant Field Values
  - BIGGER
```
public static final int BIGGER
```
    The comparison type meaning > as in ID>1.
    
    See Also:
    
    Constant Field Values
  - SMALLER_EQUAL
```
public static final int SMALLER_EQUAL
```
    The comparison type meaning <= as in ID<=1.
    
    See Also:
    
    Constant Field Values
  - SMALLER
```
public static final int SMALLER
```
    The comparison type meaning < as in ID<1.
    
    See Also:
    
    Constant Field Values
  - NOT_EQUAL
```
public static final int NOT_EQUAL
```
    The comparison type meaning <> as in ID<>1.
    
    See Also:
    
    Constant Field Values
  - NOT_EQUAL_NULL_SAFE
```
public static final int NOT_EQUAL_NULL_SAFE
```
    The comparison type meaning ID IS NOT 1 (ID IS DISTINCT FROM 1).
    
    See Also:
    
    Constant Field Values
  - IS_NULL
```
public static final int IS_NULL
```
    The comparison type meaning IS NULL as in NAME IS NULL.
    
    See Also:
    
    Constant Field Values
  - IS_NOT_NULL
```
public static final int IS_NOT_NULL
```
    The comparison type meaning IS NOT NULL as in NAME IS NOT NULL.
    
    See Also:
    
    Constant Field Values
  - FALSE
```
public static final int FALSE
```
    This is a pseudo comparison type that is only used for index conditions. It means the comparison will always yield FALSE. Example: 1=0.
    
    See Also:
    
    Constant Field Values
  - IN_LIST
```
public static final int IN_LIST
```
    This is a pseudo comparison type that is only used for index conditions. It means equals any value of a list. Example: IN(1, 2, 3).
    
    See Also:
    
    Constant Field Values
  - IN_QUERY
```
public static final int IN_QUERY
```
    This is a pseudo comparison type that is only used for index conditions. It means equals any value of a list. Example: IN(SELECT ...).
    
    See Also:
    
    Constant Field Values
  - SPATIAL_INTERSECTS
```
public static final int SPATIAL_INTERSECTS
```
    This is a comparison type that is only used for spatial index conditions (operator "&&").
    
    See Also:
    
    Constant Field Values
- Constructor Detail
  - Comparison
```
public Comparison(Session session,
                  int compareType,
                  Expression left,
                  Expression right)
```
- Method Detail
  - getSQL
```
public java.lang.String getSQL()
```
    Description copied from class: Expression
    
    Get the SQL statement of this expression. This may not always be the original SQL statement, specially after optimization.
    
    Specified by:
    
    getSQL in class Expression
    
    Returns:
    
    the SQL statement
  - optimize
```
public Expression optimize(Session session)
```
    Description copied from class: Expression
    
    Try to optimize the expression.
    
    Specified by:
    
    optimize in class Expression
    
    Parameters:
    
    session - the session
    
    Returns:
    
    the optimized expression
  - getValue
```
public Value getValue(Session session)
```
    Description copied from class: Expression
    
    Return the resulting value for the current row.
    
    Specified by:
    
    getValue in class Expression
    
    Parameters:
    
    session - the session
    
    Returns:
    
    the result
  - getNotIfPossible
```
public Expression getNotIfPossible(Session session)
```
    Description copied from class: Expression
    
    If it is possible, return the negated expression. This is used to optimize NOT expressions: NOT ID>10 can be converted to ID<=10. Returns null if negating is not possible.
    
    Overrides:
    
    getNotIfPossible in class Expression
    
    Parameters:
    
    session - the session
    
    Returns:
    
    the negated expression, or null
  - createIndexConditions
```
public void createIndexConditions(Session session,
                                  TableFilter filter)
```
    Description copied from class: Expression
    
    Create index conditions if possible and attach them to the table filter.
    
    Overrides:
    
    createIndexConditions in class Expression
    
    Parameters:
    
    session - the session
    
    filter - the table filter
  - setEvaluatable
```
public void setEvaluatable(TableFilter tableFilter,
                           boolean b)
```
    Description copied from class: Expression
    
    Tell the expression columns whether the table filter can return values now. This is used when optimizing the query.
    
    Specified by:
    
    setEvaluatable in class Expression
    
    Parameters:
    
    tableFilter - the table filter
    
    b - true if the table filter can return value
  - updateAggregate
```
public void updateAggregate(Session session)
```
    Description copied from class: Expression
    
    Update an aggregate value. This method is called at statement execution time. It is usually called once for each row, but if the expression is used multiple times (for example in the column list, and as part of the HAVING expression) it is called multiple times - the row counter needs to be used to make sure the internal state is only updated once.
    
    Specified by:
    
    updateAggregate in class Expression
    
    Parameters:
    
    session - the session
  - addFilterConditions
```
public void addFilterConditions(TableFilter filter,
                                boolean outerJoin)
```
    Description copied from class: Expression
    
    Add conditions to a table filter if they can be evaluated.
    
    Overrides:
    
    addFilterConditions in class Expression
    
    Parameters:
    
    filter - the table filter
    
    outerJoin - if the expression is part of an outer join
  - mapColumns
```
public void mapColumns(ColumnResolver resolver,
                       int level)
```
    Description copied from class: Expression
    
    Map the columns of the resolver to expression columns.
    
    Specified by:
    
    mapColumns in class Expression
    
    Parameters:
    
    resolver - the column resolver
    
    level - the subquery nesting level
  - isEverything
```
public boolean isEverything(ExpressionVisitor visitor)
```
    Description copied from class: Expression
    
    Check if this expression and all sub-expressions can fulfill a criteria. If any part returns false, the result is false.
    
    Specified by:
    
    isEverything in class Expression
    
    Parameters:
    
    visitor - the visitor
    
    Returns:
    
    if the criteria can be fulfilled
  - getCost
```
public int getCost()
```
    Description copied from class: Expression
    
    Estimate the cost to process the expression. Used when optimizing the query, to calculate the query plan with the lowest estimated cost.
    
    Specified by:
    
    getCost in class Expression
    
    Returns:
    
    the estimated cost
  - getExpression
```
public Expression getExpression(boolean getLeft)
```
    Get the left or the right sub-expression of this condition.
    
    Parameters:
    
    getLeft - true to get the left sub-expression, false to get the right sub-expression.
    
    Returns:
    
    the sub-expression
  - getType
```
public int getType()
```
    Description copied from class: Expression
    
    Return the data type. The data type may not be known before the optimization phase.
    
    Specified by:
    
    getType in class Expression
    
    Returns:
    
    the type
  - getScale
```
public int getScale()
```
    Description copied from class: Expression
    
    Get the scale of this expression.
    
    Specified by:
    
    getScale in class Expression
    
    Returns:
    
    the scale
  - getPrecision
```
public long getPrecision()
```
    Description copied from class: Expression
    
    Get the precision of this expression.
    
    Specified by:
    
    getPrecision in class Expression
    
    Returns:
    
    the precision
  - getDisplaySize
```
public int getDisplaySize()
```
    Description copied from class: Expression
    
    Get the display size of this expression.
    
    Specified by:
    
    getDisplaySize in class Expression
    
    Returns:
    
    the display size

Class Comparison

Field Summary

Constructor Summary

Method Summary

Methods inherited from class org.h2.expression.Expression

Methods inherited from class java.lang.Object

Field Detail

NULL_SAFE

EQUAL

EQUAL_NULL_SAFE

BIGGER_EQUAL

BIGGER

SMALLER_EQUAL

SMALLER

NOT_EQUAL

NOT_EQUAL_NULL_SAFE

IS_NULL

IS_NOT_NULL

FALSE

IN_LIST

IN_QUERY

SPATIAL_INTERSECTS

Constructor Detail

Comparison

Method Detail

getSQL

optimize

getValue

getNotIfPossible

createIndexConditions

setEvaluatable

updateAggregate

addFilterConditions

mapColumns

isEverything

getCost

getExpression

getType

getScale

getPrecision

getDisplaySize