dynamically set the db in a sql query

Question

I try to run the same query in several dbs in mysql:

def m=\'xxx\'
def dbs =  [\'DB05DEC05\',\'DB06DEC06\',\'DB07DEC07\',\'DB08DEC08\',\'DB09DEC09\',\'DB10DE         


        

Answer 1

The problem is that the SQL query method sees the GString, with its embedded variable references, and turns each reference into a ? in a prepared statement.

So:

sql.query("select * from table where col = ${value}")

... is equivalent to:

sql.query("select * from table where col = ?", [ value ])

But also:

sql.query("select * from ${db}.table where col = ${value}")

is equivalent to:

sql.query("select * from ?.table where col = ?", [ db, value ])

... which fails at the DB layer because the select statement is not valid.

The obvious workaround is to use the explicit prepared statement version of query().

dbs.each{ db-> 
    sql.eachRow("select * from ${db}.mail where mid=?", m, { 
       println "\t$db ${it.mid}"
    });
}

However, the Sql class gives you an expand() method, that appears to be designed for this purpose.

dbs.each{ db -> 
   sql.eachRow(
      "select * from ${Sql.expand(db)}.mail where mid=${m}", 
      { println "\t$db ${it.mid}"} );
}