How to log SQL statements in Grails

Setting

datasource {
...
logSql = true
}

in DataSource.groovy (as per these instructions) was enough to get it working in my environment. It seems that parts of the FAQ are out of date (e.g. the many-to-many columns backwards question) so this might also be something that changed in the meantime.

I find it more useful to do the following, which is to enable Hibernate's logging to log the SQL along with bind variables (so you can see the values passed into your calls, and easily replicate the SQL in your editor or otherwise).

In your Config.groovy, add the following to your log4j block:

log4j = {

    // Enable Hibernate SQL logging with param values
    trace 'org.hibernate.type'
    debug 'org.hibernate.SQL'
    //the rest of your logging config
    // ...
    }

For grails 3.*

Option #1 add the following to logback.groovy

logger("org.hibernate.SQL", DEBUG, ["STDOUT"], false)
logger("org.hibernate.type.descriptor.sql.BasicBinder", TRACE, ["STDOUT"], false)

or

Option #2 add the following to dataSource in the application.yml. However this approach does not log the parameter values

environments:
  local:
    dataSource:
        logSql: true
        formatSql: true

Try this:

log4j = {
   ...
   debug 'org.hibernate.SQL'
   trace 'org.hibernate.type.descriptor.sql.BasicBinder'
}

It avoids the performance problems of trace logging the Hibernate type package. This works with Hibernate 3.6 and above. I got this from: https://burtbeckwith.com/blog/?p=1604