SQL Expressions: Exclude CTEs from required Tables (#106479)

Fixes #105030

---------

Co-authored-by: Sam Jewell <2903904+samjewell@users.noreply.github.com>

pkg/expr/sql/parser.go

@@ -3,6 +3,7 @@ package sql
 import (
 	"fmt"
 	"sort"
+	"strings"
 
 	"github.com/dolthub/vitess/go/vt/sqlparser"
 	"github.com/grafana/grafana/pkg/infra/log"
@@ -10,7 +11,8 @@ import (
 
 var logger = log.New("sql_expr")
 
-// TablesList returns a list of tables for the sql statement
+// TablesList returns a list of tables for the sql statement excluding
+// CTEs and the 'dual' table. The list is sorted alphabetically.
 func TablesList(rawSQL string) ([]string, error) {
 	stmt, err := sqlparser.Parse(rawSQL)
 	if err != nil {
@@ -19,10 +21,18 @@ func TablesList(rawSQL string) ([]string, error) {
 	}
 
 	tables := make(map[string]struct{})
+	cteNames := make(map[string]struct{})
 
 	walkSubtree := func(node sqlparser.SQLNode) error {
 		err = sqlparser.Walk(func(node sqlparser.SQLNode) (kontinue bool, err error) {
 			switch v := node.(type) {
+			case *sqlparser.CommonTableExpr:
+				// Track CTE name from the As field
+				cteName := v.As.String()
+				if cteName != "" {
+					cteNames[strings.ToLower(cteName)] = struct{}{}
+				}
+
 			case *sqlparser.AliasedTableExpr:
 				if tableName, ok := v.Expr.(sqlparser.TableName); ok {
 					tables[tableName.Name.String()] = struct{}{}
@@ -49,9 +59,15 @@ func TablesList(rawSQL string) ([]string, error) {
 		// Remove 'dual' table if it exists
 		// This is a special table in MySQL that always returns a single row with a single column
 		// See: https://dev.mysql.com/doc/refman/5.7/en/select.html#:~:text=You%20are%20permitted%20to%20specify%20DUAL%20as%20a%20dummy%20table%20name%20in%20situations%20where%20no%20tables%20are%20referenced
-		if table != "dual" {
-			result = append(result, table)
+		if table == "dual" {
+			continue
 		}
+
+		// Skip CTEs
+		if _, ok := cteNames[strings.ToLower(table)]; ok {
+			continue
+		}
+		result = append(result, table)
 	}
 
 	sort.Strings(result)