ExpressionColumn (JBoss Application Server: Build 7.1.2.Final API)

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

```
public class ExpressionColumn
extends Expression
```
A expression that represents a column of a table or view.

Constructor Summary

Constructors
Constructor and Description
`ExpressionColumn(Database database, Column column)`
`ExpressionColumn(Database database, String schemaName, String tableAlias, String columnName)`

Method Summary

Methods
Modifier and Type	Method and Description
`void`	`createIndexConditions(Session session, TableFilter filter)` Create index conditions if possible and attach them to the table filter.
`String`	`getAlias()` Get the alias name of a column or SQL expression if it is not an aliased expression.
`Column`	`getColumn()`
`String`	`getColumnName()` Get the column name or alias name of this expression.
`int`	`getCost()` Estimate the cost to process the expression.
`int`	`getDisplaySize()` Get the display size of this expression.
`Expression`	`getNotIfPossible(Session session)` If it is possible, return the negated expression.
`int`	`getNullable()` Check whether this expression is a column and can store NULL.
`String`	`getOriginalColumnName()`
`String`	`getOriginalTableAliasName()`
`long`	`getPrecision()` Get the precision of this expression.
`int`	`getScale()` Get the scale of this expression.
`String`	`getSchemaName()` Get the schema name, or null
`String`	`getSQL()` Get the SQL statement of this expression.
`TableFilter`	`getTableFilter()`
`String`	`getTableName()` Get the table name, or null
`int`	`getType()` Return the data type.
`Value`	`getValue(Session session)` Return the resulting value for the current row.
`boolean`	`isAutoIncrement()` Check if this is an auto-increment column.
`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
addFilterConditions, getBooleanValue, getExpressionColumns, getExpressionColumns, getNonAliasExpression, getTableAlias, isConstant, isValueSet, isWildcard, toString

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

- Constructor Detail
  - ExpressionColumn
```
public ExpressionColumn(Database database,
                Column column)
```
  - ExpressionColumn
```
public ExpressionColumn(Database database,
                String schemaName,
                String tableAlias,
                String columnName)
```
- Method Detail
  - getSQL
```
public 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
  - getTableFilter
```
public TableFilter getTableFilter()
```
  - 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
  - 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
  - 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
  - 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
  - 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
  - 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
  - getColumn
```
public Column getColumn()
```
  - 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
  - getOriginalColumnName
```
public String getOriginalColumnName()
```
  - getOriginalTableAliasName
```
public String getOriginalTableAliasName()
```
  - getColumnName
```
public String getColumnName()
```
    Description copied from class: Expression
    
    Get the column name or alias name of this expression.
    
    Overrides:
    
    getColumnName in class Expression
    
    Returns:
    the column name
  - getSchemaName
```
public String getSchemaName()
```
    Description copied from class: Expression
    
    Get the schema name, or null
    
    Overrides:
    
    getSchemaName in class Expression
    
    Returns:
    the schema name
  - getTableName
```
public String getTableName()
```
    Description copied from class: Expression
    
    Get the table name, or null
    
    Overrides:
    
    getTableName in class Expression
    
    Returns:
    the table name
  - getAlias
```
public String getAlias()
```
    Description copied from class: Expression
    
    Get the alias name of a column or SQL expression if it is not an aliased expression.
    
    Overrides:
    
    getAlias in class Expression
    
    Returns:
    the alias name
  - isAutoIncrement
```
public boolean isAutoIncrement()
```
    Description copied from class: Expression
    
    Check if this is an auto-increment column.
    
    Overrides:
    
    isAutoIncrement in class Expression
    
    Returns:
    true if it is an auto-increment column
  - getNullable
```
public int getNullable()
```
    Description copied from class: Expression
    
    Check whether this expression is a column and can store NULL.
    
    Overrides:
    
    getNullable in class Expression
    
    Returns:
    whether NULL is allowed
  - 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
  - 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
  - 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

Class ExpressionColumn

Constructor Summary

Method Summary

Methods inherited from class org.h2.expression.Expression

Methods inherited from class java.lang.Object

Constructor Detail

ExpressionColumn

ExpressionColumn

Method Detail

getSQL

getTableFilter

mapColumns

optimize

updateAggregate

getValue

getType

setEvaluatable

getColumn

getScale

getPrecision

getDisplaySize

getOriginalColumnName

getOriginalTableAliasName

getColumnName

getSchemaName

getTableName

getAlias

isAutoIncrement

getNullable

isEverything

getCost

createIndexConditions

getNotIfPossible