diff --git a/README.md b/README.md
index 2aa9431..165dbda 100644
--- a/README.md
+++ b/README.md
@@ -68,6 +68,16 @@ A pre-compiled binary can be downloaded from the [releases](https://github.com/z
 ### 2) Configure
 Copy the `config.toml.sample` file as `config.toml` somewhere and edit the configuration values.
 
+Source (`[db.*]`) and result (`[results.*]`) databases are configured with a driver `type` and a `dsn`:
+
+| type | dsn |
+|------|-----|
+| `postgres` | `postgres://user:password@host:5432/dbname?sslmode=disable` |
+| `mysql` | `user:password@tcp(host:3306)/dbname` |
+| `clickhouse` | `tcp://host:9000?username=user&password=password&database=dbname` |
+
+ClickHouse v1 reads credentials and the database from query parameters. The `user@pass` format is not supported.
+
 ### 3) Setup tasks
 Write your SQL query tasks in `.sql` files in the `goyesql` format (as shown in the examples earlier) and put them in a directory somewhere.
 
diff --git a/cmd/config.sample.toml b/cmd/config.sample.toml
index c031d9c..5aa4ea4 100644
--- a/cmd/config.sample.toml
+++ b/cmd/config.sample.toml
@@ -61,6 +61,8 @@ results_table = "results_%s"
 
 # type = "postgres" dsn = "postgres://user:password@host:5432/dbname?sslmode=disable"
 # type = "mysql" dsn = "user:password@tcp(host:3306)/dbname"
+# type = "clickhouse" dsn = "tcp://host:9000?username=user&password=url-encoded-password&database=dbname"
+# IMPORTANT: clickhouse DSN requires passwords to be urlencoded if they have special characters.
 
 [db.my_db]
 type = "mysql"
diff --git a/config.toml.sample b/config.toml.sample
index 1d958a0..9d4b3d3 100644
--- a/config.toml.sample
+++ b/config.toml.sample
@@ -41,18 +41,10 @@ max_idle = 10
 max_active = 100
 connect_timeout = "10s"
 
+# URL-encode ClickHouse query values (e.g. % as %25, + as %2B).
 [db.ch_db]
 type = "clickhouse"
-dsn = "clickhouse://default:@127.0.0.1:9000/default?sslmode=disable"
+dsn = "tcp://127.0.0.1:9000?username=default&password=&database=default"
 max_idle = 10
 max_active = 100
 connect_timeout = "10s"
-# host = "localhost"
-# port = 9000
-# db = "default"
-# user = "default" 
-# password = ""
-# autocommit = false
-# max_active = 100
-# max_idle = 100
-# connect_timeout = 60
\ No newline at end of file
diff --git a/internal/dbpool/dbpool.go b/internal/dbpool/dbpool.go
index e690dd6..e486a66 100644
--- a/internal/dbpool/dbpool.go
+++ b/internal/dbpool/dbpool.go
@@ -30,7 +30,7 @@ func New(mp map[string]Config) (map[string]*sql.DB, error) {
 	for name, cfg := range mp {
 		db, err := NewConn(cfg)
 		if err != nil {
-			return nil, err
+			return nil, fmt.Errorf("db %q: %w", name, err)
 		}
 
 		out[name] = db