MergeUsing

java.lang.Object
- org.h2.command.Prepared
- - org.h2.command.dml.MergeUsing

```
public class MergeUsing
extends Prepared
```
This class represents the statement syntax MERGE table alias USING... It does not replace the existing MERGE INTO... KEYS... form. It supports the SQL 2003/2008 standard MERGE statement: http://en.wikipedia.org/wiki/Merge_%28SQL%29 Database management systems Oracle Database, DB2, Teradata, EXASOL, Firebird, CUBRID, HSQLDB, MS SQL, Vectorwise and Apache Derby & Postgres support the standard syntax of the SQL 2003/2008 MERGE command: MERGE INTO targetTable AS T USING sourceTable AS S ON (T.ID = S.ID) WHEN MATCHED THEN UPDATE SET column1 = value1 [, column2 = value2 ...] WHERE column1=valueUpdate DELETE WHERE column1=valueDelete WHEN NOT MATCHED THEN INSERT (column1 [, column2 ...]) VALUES (value1 [, value2 ...]); Only Oracle support the additional optional DELETE clause. Implementation notes: 1) The ON clause must specify 1 or more columns from the TARGET table because they are used in the plan SQL WHERE statement. Otherwise an exception is raised. 2) The ON clause must specify 1 or more columns from the SOURCE table/query because they are used to track the join key values for every source table row - to prevent any TARGET rows from being updated twice per MERGE USING statement. This is to implement a requirement from the MERGE INTO specification requiring each row from being updated more than once per MERGE USING statement. The source columns are used to gather the effective "key" values which have been updated, in order to implement this requirement. If the no SOURCE table/query columns are found in the ON clause, then an exception is raised. The update row counts of the embedded UPDATE and DELETE statements are also tracked to ensure no more than 1 row is ever updated. (Note One special case of this is that the DELETE is allowed to affect the same row which was updated by UPDATE - this is an Oracle only extension.) 3) UPDATE and DELETE statements are allowed to specify extra conditional criteria (in the WHERE clause) to allow fine-grained control of actions when a record is found. The ON clause conditions are always prepended to the WHERE clause of these embedded statements, so they will never update more than the ON join condition. 4) Previously if neither UPDATE or DELETE clause is supplied, but INSERT is supplied - the INSERT action is always triggered. This is because the embedded UPDATE and DELETE statement's returned update row count is used to detect a matching join. If neither of the two the statements are provided, no matching join is NEVER detected. A fix for this is now implemented as described below: We now generate a "matchSelect" query and use that to always detect a match join - rather than relying on UPDATE or DELETE statements. This is an improvement, especially in the case that if either of the UPDATE or DELETE statements had their own fine-grained WHERE conditions, making them completely different conditions than the plain ON condition clause which the SQL author would be specifying/expecting. An additional benefit of this solution is that this "matchSelect" query is used to return the ROWID of the found (or inserted) query - for more accurate enforcing of the only-update-each-target-row-once rule.

Field Summary
- Fields inherited from class org.h2.command.Prepared
  create, parameters, prepareAlways, session, sqlStatement

Constructor Summary

Constructors
Constructor and Description

MergeUsing(Merge merge)

Constructors
Constructor and Description
`MergeUsing(Merge merge)`

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`Prepared`	`getDeleteCommand()`
`Insert`	`getInsertCommand()`
`Expression`	`getOnCondition()`
`java.lang.String`	`getPlanSQL()` Get the SQL statement with the execution plan.
`Query`	`getQuery()`
`java.lang.String`	`getQueryAlias()`
`TableFilter`	`getSourceTableFilter()`
`Select`	`getTargetMatchQuery()`
`Table`	`getTargetTable()`
`TableFilter`	`getTargetTableFilter()`
`int`	`getType()` Get the command type as defined in CommandInterface
`Prepared`	`getUpdateCommand()`
`boolean`	`isTransactional()` Check if this command is transactional.
`protected void`	`merge(Row sourceRow)` Merge the given row.
`void`	`prepare()` Prepare this statement.
`ResultInterface`	`queryMeta()` Get an empty result set containing the meta data.
`void`	`setDeleteCommand(Delete deleteCommand)`
`void`	`setInsertCommand(Insert insertCommand)`
`void`	`setOnCondition(Expression condition)`
`void`	`setQuery(Query query)`
`void`	`setQueryAlias(java.lang.String alias)`
`void`	`setSourceTableFilter(TableFilter sourceTableFilter)`
`void`	`setTargetMatchQuery(Select targetMatchQuery)`
`void`	`setTargetTable(Table targetTable)`
`void`	`setTargetTableFilter(TableFilter targetTableFilter)`
`void`	`setUpdateCommand(Update updateCommand)`
`int`	`update()` Execute the statement.

Methods inherited from class org.h2.command.Prepared
checkCanceled, checkParameters, getCteCleanups, getCurrentObjectId, getCurrentRowNumber, getObjectId, getParameters, getSession, getSQL, getSQL, getSQL, isCacheable, isQuery, isReadOnly, needRecompile, query, setCommand, setCteCleanups, setCurrentRowNumber, setObjectId, setParameterList, setPrepareAlways, setRow, setSession, setSQL, toString

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

- Constructor Detail
  - MergeUsing
```
public MergeUsing(Merge merge)
```
- Method Detail
  - update
```
public int update()
```
    Description copied from class: Prepared
    
    Execute the statement.
    
    Overrides:
    
    update in class Prepared
    
    Returns:
    
    the update count
  - merge
```
protected void merge(Row sourceRow)
```
    Merge the given row.
    
    Parameters:
    
    sourceRow - the row
  - getPlanSQL
```
public java.lang.String getPlanSQL()
```
    Description copied from class: Prepared
    
    Get the SQL statement with the execution plan.
    
    Overrides:
    
    getPlanSQL in class Prepared
    
    Returns:
    
    the execution plan
  - prepare
```
public void prepare()
```
    Description copied from class: Prepared
    
    Prepare this statement.
    
    Overrides:
    
    prepare in class Prepared
  - setSourceTableFilter
```
public void setSourceTableFilter(TableFilter sourceTableFilter)
```
  - getSourceTableFilter
```
public TableFilter getSourceTableFilter()
```
  - setOnCondition
```
public void setOnCondition(Expression condition)
```
  - getOnCondition
```
public Expression getOnCondition()
```
  - getUpdateCommand
```
public Prepared getUpdateCommand()
```
  - setUpdateCommand
```
public void setUpdateCommand(Update updateCommand)
```
  - getDeleteCommand
```
public Prepared getDeleteCommand()
```
  - setDeleteCommand
```
public void setDeleteCommand(Delete deleteCommand)
```
  - getInsertCommand
```
public Insert getInsertCommand()
```
  - setInsertCommand
```
public void setInsertCommand(Insert insertCommand)
```
  - setQueryAlias
```
public void setQueryAlias(java.lang.String alias)
```
  - getQueryAlias
```
public java.lang.String getQueryAlias()
```
  - getQuery
```
public Query getQuery()
```
  - setQuery
```
public void setQuery(Query query)
```
  - setTargetTableFilter
```
public void setTargetTableFilter(TableFilter targetTableFilter)
```
  - getTargetTableFilter
```
public TableFilter getTargetTableFilter()
```
  - getTargetTable
```
public Table getTargetTable()
```
  - setTargetTable
```
public void setTargetTable(Table targetTable)
```
  - getTargetMatchQuery
```
public Select getTargetMatchQuery()
```
  - setTargetMatchQuery
```
public void setTargetMatchQuery(Select targetMatchQuery)
```
  - isTransactional
```
public boolean isTransactional()
```
    Description copied from class: Prepared
    
    Check if this command is transactional. If it is not, then it forces the current transaction to commit.
    
    Specified by:
    
    isTransactional in class Prepared
    
    Returns:
    
    true if it is
  - queryMeta
```
public ResultInterface queryMeta()
```
    Description copied from class: Prepared
    
    Get an empty result set containing the meta data.
    
    Specified by:
    
    queryMeta in class Prepared
    
    Returns:
    
    the result set
  - getType
```
public int getType()
```
    Description copied from class: Prepared
    
    Get the command type as defined in CommandInterface
    
    Specified by:
    
    getType in class Prepared
    
    Returns:
    
    the statement type

Class MergeUsing

Field Summary

Fields inherited from class org.h2.command.Prepared

Constructor Summary

Method Summary

Methods inherited from class org.h2.command.Prepared

Methods inherited from class java.lang.Object

Constructor Detail

MergeUsing

Method Detail

update

merge

getPlanSQL

prepare

setSourceTableFilter

getSourceTableFilter

setOnCondition

getOnCondition

getUpdateCommand

setUpdateCommand

getDeleteCommand

setDeleteCommand

getInsertCommand

setInsertCommand

setQueryAlias

getQueryAlias

getQuery

setQuery

setTargetTableFilter

getTargetTableFilter

getTargetTable

setTargetTable

getTargetMatchQuery

setTargetMatchQuery

isTransactional

queryMeta

getType