Add set ∋ / ∌ to SQL where clauses

sql/select.go

@@ -90,7 +90,7 @@ func (p *Parser) parseWhere() (Expr, error) {
 		}
 		w.LHS = declare(tok, lit)
 
-		tok, lit, err = p.shouldBe(IN, EQ, NEQ, GT, LT, GTE, LTE, EQR, NER)
+		tok, lit, err = p.shouldBe(IN, EQ, NEQ, GT, LT, GTE, LTE, EQR, NER, SEQ, SNE)
 		if err != nil {
 			return nil, err
 		}

sql/sql_test.go

@@ -306,7 +306,7 @@ func Test_Parse_Queries_Select(t *testing.T) {
 		},
 		{
 			sql: "SELECT * FROM person WHERE id",
-			err: "found `` but expected `IN, =, !=, >, <, >=, <=, =~, !~`",
+			err: "found `` but expected `IN, =, !=, >, <, >=, <=, =~, !~, ∋, ∌`",
 		},
 		{
 			sql: "SELECT * FROM person WHERE id =",

sql/token.go

@@ -73,6 +73,8 @@ const (
 	GTE // >=
 	EQR // =~
 	NER // !~
+	SEQ // ∋
+	SNE // ∌
 
 	operatorEnd
 
@@ -176,6 +178,8 @@ var tokens = [...]string{
 	GTE: ">=",
 	EQR: "=~",
 	NER: "!~",
+	SEQ: "∋",
+	SNE: "∌",
 
 	// keywords