Multiple queries executed in java in single statement
Based on my testing, the correct flag is "allowMultiQueries=true"
You can use Batch update but queries must be action(i.e. insert,update and delete) queries
Statement s = c.createStatement();
String s1 = "update emp set name='abc' where salary=984";
String s2 = "insert into emp values ('Osama',1420)";
s.addBatch(s1);
s.addBatch(s2);
s.executeBatch();
I was wondering if it is possible to execute something like this using JDBC.
"SELECT FROM * TABLE;INSERT INTO TABLE;"
Yes it is possible. There are two ways, as far as I know. They are
- By setting database connection property to allow multiple queries, separated by a semi-colon by default.
- By calling a stored procedure that returns cursors implicit.
Following examples demonstrate the above two possibilities.
Example 1: ( To allow multiple queries ):
While sending a connection request, you need to append a connection property allowMultiQueries=true
to the database url. This is additional connection property to those if already exists some, like autoReConnect=true
, etc.. Acceptable values for allowMultiQueries
property are true
, false
, yes
, and no
. Any other value is rejected at runtime with an SQLException
.
String dbUrl = "jdbc:mysql:///test?allowMultiQueries=true";
Unless such instruction is passed, an SQLException
is thrown.
You have to use execute( String sql )
or its other variants to fetch results of the query execution.
boolean hasMoreResultSets = stmt.execute( multiQuerySqlString );
To iterate through and process results you require following steps:
READING_QUERY_RESULTS: // label
while ( hasMoreResultSets || stmt.getUpdateCount() != -1 ) {
if ( hasMoreResultSets ) {
Resultset rs = stmt.getResultSet();
// handle your rs here
} // if has rs
else { // if ddl/dml/...
int queryResult = stmt.getUpdateCount();
if ( queryResult == -1 ) { // no more queries processed
break READING_QUERY_RESULTS;
} // no more queries processed
// handle success, failure, generated keys, etc here
} // if ddl/dml/...
// check to continue in the loop
hasMoreResultSets = stmt.getMoreResults();
} // while results
Example 2: Steps to follow:
- Create a procedure with one or more
select
, andDML
queries. - Call it from java using
CallableStatement
. - You can capture multiple
ResultSet
s executed in procedure.
DML results can't be captured but can issue anotherselect
to find how the rows are affected in the table.
Sample table and procedure:
mysql> create table tbl_mq( i int not null auto_increment, name varchar(10), primary key (i) );
Query OK, 0 rows affected (0.16 sec)
mysql> delimiter //
mysql> create procedure multi_query()
-> begin
-> select count(*) as name_count from tbl_mq;
-> insert into tbl_mq( names ) values ( 'ravi' );
-> select last_insert_id();
-> select * from tbl_mq;
-> end;
-> //
Query OK, 0 rows affected (0.02 sec)
mysql> delimiter ;
mysql> call multi_query();
+------------+
| name_count |
+------------+
| 0 |
+------------+
1 row in set (0.00 sec)
+------------------+
| last_insert_id() |
+------------------+
| 3 |
+------------------+
1 row in set (0.00 sec)
+---+------+
| i | name |
+---+------+
| 1 | ravi |
+---+------+
1 row in set (0.00 sec)
Query OK, 0 rows affected (0.00 sec)
Call Procedure from Java:
CallableStatement cstmt = con.prepareCall( "call multi_query()" );
boolean hasMoreResultSets = cstmt.execute();
READING_QUERY_RESULTS:
while ( hasMoreResultSets ) {
Resultset rs = stmt.getResultSet();
// handle your rs here
} // while has more rs
Hint: If you have more than one connection property then separate them with:
&
To give you somthing like:
url="jdbc:mysql://localhost/glyndwr?autoReconnect=true&allowMultiQueries=true"
I hope this helps some one.
Regards,
Glyn