Select (H2 Database Engine wt-1.0.1 API)

java.lang.Object
- org.h2.command.Prepared
- - org.h2.command.dml.Query
  - - org.h2.command.dml.Select

```
public class Select
extends Query
```
This class represents a simple SELECT statement. For each select statement, visibleColumnCount <= distinctColumnCount <= expressionCount. The expression list count could include ORDER BY and GROUP BY expressions that are not in the select list. The call sequence is init(), mapColumns() if it's a subquery, prepare().

作者:

Thomas Mueller, Joel Turkel (Group sorted query)

字段概要
- 从类继承的字段 org.h2.command.dml.Query
  distinct, limitExpr, offsetExpr, randomAccessResult, sampleSizeExpr
- 从类继承的字段 org.h2.command.Prepared
  create, parameters, prepareAlways, session, sqlStatement

构造器概要

构造器
构造器和说明

Select(Session session)

构造器
构造器和说明
`Select(Session session)`

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
`void`	`addCondition(Expression cond)` Add a condition to the list of conditions.
`void`	`addGlobalCondition(Parameter param, int columnId, int comparisonType)` Add a condition to the query.
`void`	`addTableFilter(TableFilter filter, boolean isTop)` Add a table to the query.
`boolean`	`allowGlobalConditions()` Check whether adding condition to the query is allowed.
`void`	`fireBeforeSelectTriggers()` Call the before triggers on all tables.
`int`	`getColumnCount()` Get the column count of this query.
`double`	`getCost()` Calculate the cost to execute this query.
`HashMap<Expression,Object>`	`getCurrentGroup()`
`int`	`getCurrentGroupRowId()`
`ArrayList<Expression>`	`getExpressions()` The the list of select expressions.
`ArrayList<Expression>`	`getGroupBy()`
`Expression`	`getHaving()`
`JoinBatch`	`getJoinBatch()`
`String`	`getPlanSQL()` Get the SQL statement with the execution plan.
`SortOrder`	`getSortOrder()`
`HashSet<Table>`	`getTables()` Get all tables that are involved in this query.
`ArrayList<TableFilter>`	`getTopFilters()`
`TableFilter`	`getTopTableFilter()`
`int`	`getType()` Get the command type as defined in CommandInterface
`boolean`	`hasOrder()` Whether the query has an order.
`void`	`init()` Initialize the query.
`boolean`	`isCacheable()`
`boolean`	`isEverything(ExpressionVisitor visitor)` Check if this expression and all sub-expressions can fulfill a criteria.
`boolean`	`isQuickAggregateQuery()` Check if this is an aggregate query with direct lookup, for example a query of the type SELECT COUNT(*) FROM TEST or SELECT MAX(ID) FROM TEST.
`boolean`	`isReadOnly()` Check if this command is read only.
`boolean`	`isUnion()` Check if this is a UNION query.
`void`	`mapColumns(ColumnResolver resolver, int level)` Map the columns to the given column resolver.
`void`	`prepare()` Prepare this statement.
`void`	`prepareJoinBatch()` Prepare join batching.
`ResultInterface`	`queryMeta()` Get an empty result set containing the meta data.
`protected LocalResult`	`queryWithoutCache(int maxRows, ResultTarget target)` Execute the query without checking the cache.
`void`	`setEvaluatable(TableFilter tableFilter, boolean b)` Change the evaluatable flag.
`void`	`setExpressions(ArrayList<Expression> expressions)`
`void`	`setForUpdate(boolean b)` Set the 'for update' flag.
`void`	`setGroupBy(ArrayList<Expression> group)`
`void`	`setGroupQuery()` Called if this query contains aggregate functions.
`void`	`setHaving(Expression having)`
`void`	`setOrder(ArrayList<SelectOrderBy> order)` Set the order by list.
`void`	`updateAggregate(Session s)` Update all aggregate function values.

从类继承的方法 org.h2.command.dml.Query
disableCache, getCostAsExpression, getLimit, getMaxDataModificationId, getOffset, getParameterValues, isDistinct, isQuery, isTransactional, prepareOrder, query, setDistinct, setLimit, setOffset, setRandomAccessResult, setSampleSize

从类继承的方法 org.h2.command.Prepared
checkCanceled, checkParameters, getCurrentObjectId, getCurrentRowNumber, getObjectId, getParameters, getSQL, getSQL, getSQL, needRecompile, setCommand, setCurrentRowNumber, setObjectId, setParameterList, setPrepareAlways, setRow, setSession, setSQL, toString, update

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

- 构造器详细资料
  - Select
```
public Select(Session session)
```
- 方法详细资料
  - isUnion
```
public boolean isUnion()
```
    从类复制的说明: Query
    
    Check if this is a UNION query.
    
    指定者:
    
    isUnion 在类中 Query
    
    返回:
    
    true if this is a UNION query
  - addTableFilter
```
public void addTableFilter(TableFilter filter,
                           boolean isTop)
```
    Add a table to the query.
    
    参数:
    
    filter - the table to add
    
    isTop - if the table can be the first table in the query plan
  - getTopFilters
```
public ArrayList<TableFilter> getTopFilters()
```
  - setExpressions
```
public void setExpressions(ArrayList<Expression> expressions)
```
  - setGroupQuery
```
public void setGroupQuery()
```
    Called if this query contains aggregate functions.
  - setGroupBy
```
public void setGroupBy(ArrayList<Expression> group)
```
  - getGroupBy
```
public ArrayList<Expression> getGroupBy()
```
  - getCurrentGroup
```
public HashMap<Expression,Object> getCurrentGroup()
```
  - getCurrentGroupRowId
```
public int getCurrentGroupRowId()
```
  - setOrder
```
public void setOrder(ArrayList<SelectOrderBy> order)
```
    从类复制的说明: Query
    
    Set the order by list.
    
    指定者:
    
    setOrder 在类中 Query
    
    参数:
    
    order - the order by list
  - hasOrder
```
public boolean hasOrder()
```
    从类复制的说明: Query
    
    Whether the query has an order.
    
    指定者:
    
    hasOrder 在类中 Query
    
    返回:
    
    true if it has
  - addCondition
```
public void addCondition(Expression cond)
```
    Add a condition to the list of conditions.
    
    参数:
    
    cond - the condition to add
  - queryMeta
```
public ResultInterface queryMeta()
```
    从类复制的说明: Prepared
    
    Get an empty result set containing the meta data.
    
    指定者:
    
    queryMeta 在类中 Prepared
    
    返回:
    
    the result set
  - queryWithoutCache
```
protected LocalResult queryWithoutCache(int maxRows,
                                        ResultTarget target)
```
    从类复制的说明: Query
    
    Execute the query without checking the cache. If a target is specified, the results are written to it, and the method returns null. If no target is specified, a new LocalResult is created and returned.
    
    指定者:
    
    queryWithoutCache 在类中 Query
    
    参数:
    
    maxRows - the limit as specified in the JDBC method call
    
    target - the target to write results to
    
    返回:
    
    the result
  - init
```
public void init()
```
    从类复制的说明: Query
    
    Initialize the query.
    
    指定者:
    
    init 在类中 Query
  - prepare
```
public void prepare()
```
    从类复制的说明: Prepared
    
    Prepare this statement.
    
    覆盖:
    
    prepare 在类中 Prepared
  - prepareJoinBatch
```
public void prepareJoinBatch()
```
    从类复制的说明: Query
    
    Prepare join batching.
    
    指定者:
    
    prepareJoinBatch 在类中 Query
  - getJoinBatch
```
public JoinBatch getJoinBatch()
```
  - getCost
```
public double getCost()
```
    从类复制的说明: Query
    
    Calculate the cost to execute this query.
    
    指定者:
    
    getCost 在类中 Query
    
    返回:
    
    the cost
  - getTables
```
public HashSet<Table> getTables()
```
    从类复制的说明: Query
    
    Get all tables that are involved in this query.
    
    指定者:
    
    getTables 在类中 Query
    
    返回:
    
    the set of tables
  - fireBeforeSelectTriggers
```
public void fireBeforeSelectTriggers()
```
    从类复制的说明: Query
    
    Call the before triggers on all tables.
    
    指定者:
    
    fireBeforeSelectTriggers 在类中 Query
  - getPlanSQL
```
public String getPlanSQL()
```
    从类复制的说明: Prepared
    
    Get the SQL statement with the execution plan.
    
    覆盖:
    
    getPlanSQL 在类中 Prepared
    
    返回:
    
    the execution plan
  - setHaving
```
public void setHaving(Expression having)
```
  - getHaving
```
public Expression getHaving()
```
  - getColumnCount
```
public int getColumnCount()
```
    从类复制的说明: Query
    
    Get the column count of this query.
    
    指定者:
    
    getColumnCount 在类中 Query
    
    返回:
    
    the column count
  - getTopTableFilter
```
public TableFilter getTopTableFilter()
```
  - getExpressions
```
public ArrayList<Expression> getExpressions()
```
    从类复制的说明: Query
    
    The the list of select expressions. This may include invisible expressions such as order by expressions.
    
    指定者:
    
    getExpressions 在类中 Query
    
    返回:
    
    the list of expressions
  - setForUpdate
```
public void setForUpdate(boolean b)
```
    从类复制的说明: Query
    
    Set the 'for update' flag.
    
    指定者:
    
    setForUpdate 在类中 Query
    
    参数:
    
    b - the new setting
  - mapColumns
```
public void mapColumns(ColumnResolver resolver,
                       int level)
```
    从类复制的说明: Query
    
    Map the columns to the given column resolver.
    
    指定者:
    
    mapColumns 在类中 Query
    
    参数:
    
    resolver - the resolver
    
    level - the subquery level (0 is the top level query, 1 is the first subquery level)
  - setEvaluatable
```
public void setEvaluatable(TableFilter tableFilter,
                           boolean b)
```
    从类复制的说明: Query
    
    Change the evaluatable flag. This is used when building the execution plan.
    
    指定者:
    
    setEvaluatable 在类中 Query
    
    参数:
    
    tableFilter - the table filter
    
    b - the new value
  - isQuickAggregateQuery
```
public boolean isQuickAggregateQuery()
```
    Check if this is an aggregate query with direct lookup, for example a query of the type SELECT COUNT(*) FROM TEST or SELECT MAX(ID) FROM TEST.
    
    返回:
    
    true if a direct lookup is possible
  - addGlobalCondition
```
public void addGlobalCondition(Parameter param,
                               int columnId,
                               int comparisonType)
```
    从类复制的说明: Query
    
    Add a condition to the query. This is used for views.
    
    指定者:
    
    addGlobalCondition 在类中 Query
    
    参数:
    
    param - the parameter
    
    columnId - the column index (0 meaning the first column)
    
    comparisonType - the comparison type
  - updateAggregate
```
public void updateAggregate(Session s)
```
    从类复制的说明: Query
    
    Update all aggregate function values.
    
    指定者:
    
    updateAggregate 在类中 Query
    
    参数:
    
    s - the session
  - isEverything
```
public boolean isEverything(ExpressionVisitor visitor)
```
    从类复制的说明: Query
    
    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 Query
    
    参数:
    
    visitor - the visitor
    
    返回:
    
    if the criteria can be fulfilled
  - isReadOnly
```
public boolean isReadOnly()
```
    从类复制的说明: Prepared
    
    Check if this command is read only.
    
    覆盖:
    
    isReadOnly 在类中 Prepared
    
    返回:
    
    true if it is
  - isCacheable
```
public boolean isCacheable()
```
    覆盖:
    
    isCacheable 在类中 Prepared
  - getType
```
public int getType()
```
    从类复制的说明: Prepared
    
    Get the command type as defined in CommandInterface
    
    指定者:
    
    getType 在类中 Prepared
    
    返回:
    
    the statement type
  - allowGlobalConditions
```
public boolean allowGlobalConditions()
```
    从类复制的说明: Query
    
    Check whether adding condition to the query is allowed. This is not allowed for views that have an order by and a limit, as it would affect the returned results.
    
    指定者:
    
    allowGlobalConditions 在类中 Query
    
    返回:
    
    true if adding global conditions is allowed
  - getSortOrder
```
public SortOrder getSortOrder()
```

类 Select

字段概要

从类继承的字段 org.h2.command.dml.Query

从类继承的字段 org.h2.command.Prepared

构造器概要

方法概要

从类继承的方法 org.h2.command.dml.Query

从类继承的方法 org.h2.command.Prepared

从类继承的方法 java.lang.Object

构造器详细资料

Select

方法详细资料

isUnion

addTableFilter

getTopFilters

setExpressions

setGroupQuery

setGroupBy

getGroupBy

getCurrentGroup

getCurrentGroupRowId

setOrder

hasOrder

addCondition

queryMeta

queryWithoutCache

init

prepare

prepareJoinBatch

getJoinBatch

getCost

getTables

fireBeforeSelectTriggers

getPlanSQL

setHaving

getHaving

getColumnCount

getTopTableFilter

getExpressions

setForUpdate

mapColumns

setEvaluatable

isQuickAggregateQuery

addGlobalCondition

updateAggregate

isEverything

isReadOnly

isCacheable

getType

allowGlobalConditions

getSortOrder