chore(embedded/sql): Add support for simple CASE statements

Signed-off-by: Stefano Scafiti <[email protected]>

Author: ostafen

embedded/sql/engine_test.go

@@ -2973,13 +2973,13 @@ func TestQuery(t *testing.T) {
 			`SELECT
 				department,
 				job_title,
-				CASE
-					WHEN department = 'sales' THEN
+				CASE department
+					WHEN 'sales' THEN
 						CASE
 							WHEN job_title = 'manager' THEN '20% Bonus'
 							ELSE '10% Bonus'
 						END
-					WHEN department = 'engineering' THEN
+					WHEN 'engineering' THEN
 						CASE
 							WHEN job_title = 'senior engineer' THEN '15% Bonus'
 							ELSE '5% Bonus'

embedded/sql/parser_test.go

@@ -1674,6 +1674,57 @@ func TestParseExp(t *testing.T) {
 				}},
 			expectedError: nil,
 		},
+		{
+			input: "SELECT CASE 1 + 1 WHEN 2 THEN 1 ELSE 0 END FROM my_table",
+			expectedOutput: []SQLStmt{
+				&SelectStmt{
+					ds: &tableRef{table: "my_table"},
+					targets: []TargetEntry{
+						{
+							Exp: &CaseWhenExp{
+								exp: &NumExp{
+									op:    ADDOP,
+									left:  &Integer{1},
+									right: &Integer{1},
+								},
+								whenThen: []whenThenClause{
+									{
+										when: &Integer{2},
+										then: &Integer{1},
+									},
+								},
+								elseExp: &Integer{0},
+							},
+						},
+					},
+				},
+			},
+		},
+		{
+			input: "SELECT CASE WHEN is_deleted OR is_expired THEN 1 END AS is_deleted_or_expired FROM my_table",
+			expectedOutput: []SQLStmt{
+				&SelectStmt{
+					ds: &tableRef{table: "my_table"},
+					targets: []TargetEntry{
+						{
+							Exp: &CaseWhenExp{
+								whenThen: []whenThenClause{
+									{
+										when: &BinBoolExp{
+											op:    OR,
+											left:  &ColSelector{col: "is_deleted"},
+											right: &ColSelector{col: "is_expired"},
+										},
+										then: &Integer{1},
+									},
+								},
+							},
+							As: "is_deleted_or_expired",
+						},
+					},
+				},
+			},
+		},
 		{
 			input: "SELECT CASE WHEN is_deleted OR is_expired THEN 1 END AS is_deleted_or_expired FROM my_table",
 			expectedOutput: []SQLStmt{

embedded/sql/sql_grammar.y

@@ -136,7 +136,7 @@ func setResult(l yyLexer, stmts []SQLStmt) {
 %type <join> join
 %type <joinType> opt_join_type
 %type <checks> opt_checks
-%type <exp> exp opt_where opt_having boundexp opt_else when_then_else
+%type <exp> exp opt_exp opt_where opt_having boundexp opt_else
 %type <binExp> binExp
 %type <cols> opt_groupby
 %type <exp> opt_limit opt_offset case_when_exp
@@ -1057,6 +1057,17 @@ opt_checks:
         $$ = append([]CheckConstraint{{name: $2, exp: $4}}, $6...)
     }
 
+opt_exp:
+    {
+        $$ = nil
+    }
+|
+    exp
+    {
+        $$ = $1
+    }
+;
+
 exp:
     boundexp
     {
@@ -1104,18 +1115,12 @@ exp:
     }
 
 case_when_exp:
-    CASE when_then_else END
-    {
-        $$ = $2
-    }
-;
-
-when_then_else:
-    when_then_clauses opt_else
+    CASE opt_exp when_then_clauses opt_else END
     {
         $$ = &CaseWhenExp{
-            whenThen: $1,
-            elseExp: $2, 
+            exp: $2,
+            whenThen: $3,
+            elseExp: $4,
         }
     }
 ;