Why this error happens with groovy sql jdbc builder? - sql

Question

Why this code does not get the string for sql.execute("$y")?
import groovy.sql.Sql
def sql = Sql.newInstance("jdbc:mysql://localhost", "root","password", "com.mysql.jdbc.Driver")
def y= "select * from table"
table(sql,y)
def table(sql,x){
println ("$x")
sql.execute("$x")
}
The Output:
'select * from table'
Sep 02, 2017 3:49:39 PM groovy.sql.Sql$AbstractQueryCommand execute
WARNING: Failed to execute: ? because: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near ''select * from table'' at line 1
Caught: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near ''select * from table'' at line 1
com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near ''select * from table'' at line 1

Answer 1

sql.execute("$x")
in groovy double-quoted string with $expression inside is actually a groovy.lang.GString
so you are calling this method: Sql.execute(Gstring query)
this method replaces all $expressions in groovy string with ?
creates prepared statement and pass all $expressions as parameters of this prepared statement
in your case "$x" converted to "?" and executed.
Mysql tries to parse this query "?" and gives you an error:
MySQLSyntaxErrorException: You have an error in your SQL syntax
if you change your code to this:
sql.execute("$x" as String)
You'll beat this problem but you will face another one: you can't select rows with method Sql.execute(...)
examples with parameters
The following commands are equivalent:
def rows = sql.rows("select * from mytable where fieldA = $value")
def rows = sql.rows("select * from mytable where fieldA = ?", [value] )
def parms = [VALUE: value]
def rows = sql.rows(parms, "select * from mytable where fieldA = :VALUE")
all of them will be executed as a prepared statement "select * from mytable where fieldA = ?"

Answer 2

This problem solved by the method shown below.
import groovy.sql.Sql
def sql = Sql.newInstance("jdbc:mysql://localhost", "root","password", "com.mysql.jdbc.Driver")
def y= "select * from tablename"
table(sql,y)
def table(sql,x){
println (x)
sql.execute(x)
}
"select * from table" query can't work. Because table is a keyword in sql.
This simple change works without any errors. Thanks for your responses.