Operation (H2 Database Engine wt-1.0.1 API)

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

```
public class Operation
extends Expression
```
A mathematical expression, or string concatenation.

字段概要

字段
限定符和类型	字段和说明
`static int`	`CONCAT` This operation represents a string concatenation as in 'Hello' \|\| 'World'.
`static int`	`DIVIDE` This operation represents a division as in 4 * 2.
`static int`	`MINUS` This operation represents a subtraction as in 2 - 1.
`static int`	`MODULUS` This operation represents a modulus as in 5 % 2.
`static int`	`MULTIPLY` This operation represents a multiplication as in 2 * 3.
`static int`	`NEGATE` This operation represents a negation as in - ID.
`static int`	`PLUS` This operation represents an addition as in 1 + 2.

构造器概要

构造器
构造器和说明

Operation(int opType, Expression left, Expression right)

构造器
构造器和说明
`Operation(int opType, Expression left, Expression right)`

方法概要

所有方法实例方法具体方法
限定符和类型	方法和说明
`int`	`getCost()` Estimate the cost to process the expression.
`int`	`getDisplaySize()` Get the display size of this expression.
`long`	`getPrecision()` Get the precision of this expression.
`int`	`getScale()` Get the scale of this expression.
`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.

从类继承的方法 org.h2.expression.Expression
addFilterConditions, createIndexConditions, getAlias, getBooleanValue, getColumnName, getExpressionColumns, getExpressionColumns, getNonAliasExpression, getNotIfPossible, getNullable, getSchemaName, getTableAlias, getTableName, isAutoIncrement, isConstant, isValueSet, isWildcard, toString

从类继承的方法 java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- 字段详细资料
  - CONCAT
```
public static final int CONCAT
```
    This operation represents a string concatenation as in 'Hello' || 'World'.
    
    另请参阅:
    
    常量字段值
  - PLUS
```
public static final int PLUS
```
    This operation represents an addition as in 1 + 2.
    
    另请参阅:
    
    常量字段值
  - MINUS
```
public static final int MINUS
```
    This operation represents a subtraction as in 2 - 1.
    
    另请参阅:
    
    常量字段值
  - MULTIPLY
```
public static final int MULTIPLY
```
    This operation represents a multiplication as in 2 * 3.
    
    另请参阅:
    
    常量字段值
  - DIVIDE
```
public static final int DIVIDE
```
    This operation represents a division as in 4 * 2.
    
    另请参阅:
    
    常量字段值
  - NEGATE
```
public static final int NEGATE
```
    This operation represents a negation as in - ID.
    
    另请参阅:
    
    常量字段值
  - MODULUS
```
public static final int MODULUS
```
    This operation represents a modulus as in 5 % 2.
    
    另请参阅:
    
    常量字段值
- 构造器详细资料
  - Operation
```
public Operation(int opType,
                 Expression left,
                 Expression right)
```
- 方法详细资料
  - getSQL
```
public String getSQL()
```
    从类复制的说明: Expression
    
    Get the SQL statement of this expression. This may not always be the original SQL statement, specially after optimization.
    
    指定者:
    
    getSQL 在类中 Expression
    
    返回:
    
    the SQL statement
  - getValue
```
public Value getValue(Session session)
```
    从类复制的说明: Expression
    
    Return the resulting value for the current row.
    
    指定者:
    
    getValue 在类中 Expression
    
    参数:
    
    session - the session
    
    返回:
    
    the result
  - mapColumns
```
public void mapColumns(ColumnResolver resolver,
                       int level)
```
    从类复制的说明: Expression
    
    Map the columns of the resolver to expression columns.
    
    指定者:
    
    mapColumns 在类中 Expression
    
    参数:
    
    resolver - the column resolver
    
    level - the subquery nesting level
  - optimize
```
public Expression optimize(Session session)
```
    从类复制的说明: Expression
    
    Try to optimize the expression.
    
    指定者:
    
    optimize 在类中 Expression
    
    参数:
    
    session - the session
    
    返回:
    
    the optimized expression
  - setEvaluatable
```
public void setEvaluatable(TableFilter tableFilter,
                           boolean b)
```
    从类复制的说明: Expression
    
    Tell the expression columns whether the table filter can return values now. This is used when optimizing the query.
    
    指定者:
    
    setEvaluatable 在类中 Expression
    
    参数:
    
    tableFilter - the table filter
    
    b - true if the table filter can return value
  - getType
```
public int getType()
```
    从类复制的说明: Expression
    
    Return the data type. The data type may not be known before the optimization phase.
    
    指定者:
    
    getType 在类中 Expression
    
    返回:
    
    the type
  - getPrecision
```
public long getPrecision()
```
    从类复制的说明: Expression
    
    Get the precision of this expression.
    
    指定者:
    
    getPrecision 在类中 Expression
    
    返回:
    
    the precision
  - getDisplaySize
```
public int getDisplaySize()
```
    从类复制的说明: Expression
    
    Get the display size of this expression.
    
    指定者:
    
    getDisplaySize 在类中 Expression
    
    返回:
    
    the display size
  - getScale
```
public int getScale()
```
    从类复制的说明: Expression
    
    Get the scale of this expression.
    
    指定者:
    
    getScale 在类中 Expression
    
    返回:
    
    the scale
  - updateAggregate
```
public void updateAggregate(Session session)
```
    从类复制的说明: 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.
    
    指定者:
    
    updateAggregate 在类中 Expression
    
    参数:
    
    session - the session
  - isEverything
```
public boolean isEverything(ExpressionVisitor visitor)
```
    从类复制的说明: Expression
    
    Check if this expression and all sub-expressions can fulfill a criteria. If any part returns false, the result is false.
    
    指定者:
    
    isEverything 在类中 Expression
    
    参数:
    
    visitor - the visitor
    
    返回:
    
    if the criteria can be fulfilled
  - getCost
```
public int getCost()
```
    从类复制的说明: Expression
    
    Estimate the cost to process the expression. Used when optimizing the query, to calculate the query plan with the lowest estimated cost.
    
    指定者:
    
    getCost 在类中 Expression
    
    返回:
    
    the estimated cost

类 Operation

字段概要

构造器概要

方法概要

从类继承的方法 org.h2.expression.Expression

从类继承的方法 java.lang.Object

字段详细资料

CONCAT

PLUS

MINUS

MULTIPLY

DIVIDE

NEGATE

MODULUS

构造器详细资料

Operation

方法详细资料

getSQL

getValue

mapColumns

optimize

setEvaluatable

getType

getPrecision

getDisplaySize

getScale

updateAggregate

isEverything

getCost