Adding From to Update builder.

Author: henvic

update.go

@@ -12,6 +12,7 @@ type UpdateBuilder struct {
 	prefixes   []SQLizer
 	table      string
 	setClauses []setClause
+	fromParts  []SQLizer
 	whereParts []SQLizer
 	orderBys   []string
 	returning  []SQLizer
@@ -70,6 +71,14 @@ func (b UpdateBuilder) SQL() (sqlStr string, args []any, err error) {
 	}
 	sql.WriteString(strings.Join(setSQLs, ", "))
 
+	if len(b.fromParts) > 0 {
+		sql.WriteString(" FROM ")
+		args, err = appendSQL(b.fromParts, sql, ", ", args)
+		if err != nil {
+			return
+		}
+	}
+
 	if len(b.whereParts) > 0 {
 		sql.WriteString(" WHERE ")
 		args, err = appendSQL(b.whereParts, sql, " AND ", args)
@@ -153,6 +162,26 @@ func (b UpdateBuilder) SetMap(clauses map[string]any) UpdateBuilder {
 	return b
 }
 
+// From adds FROM expressions to the query.
+//
+// A table expression allowing columns from other tables to appear in the WHERE condition and update expressions.
+// This uses the same syntax as the FROM clause of a SELECT statement.
+// Do not repeat the target table unless you intend a self-join (in which case, you must use an alias).
+func (b UpdateBuilder) From(items ...string) UpdateBuilder {
+	parts := make([]SQLizer, 0, len(items))
+	for _, str := range items {
+		parts = append(parts, newPart(str))
+	}
+	b.fromParts = append(b.fromParts, parts...)
+	return b
+}
+
+// FromSelect adds FROM expressions to the query similar to From, but takes a Select statement.
+func (b UpdateBuilder) FromSelect(from SelectBuilder, alias string) UpdateBuilder {
+	b.fromParts = append(b.fromParts, Alias{Expr: from, As: alias})
+	return b
+}
+
 // Where adds WHERE expressions to the query.
 //
 // See SelectBuilder.Where for more information.

update_test.go

@@ -103,6 +103,28 @@ func TestUpdateBuilderSQL(t *testing.T) {
 				"RETURNING (SELECT abc FROM atable) AS something",
 			wantArgs: []any{0, 1, 2, "foo", "bar", 3},
 		},
+		{
+			name: "from",
+			b: Update("employees").Set("sales_count", Expr("sales_count + 1")).From("accounts").
+				Where("accounts.name = ?", "Acme Corporation").
+				Where("employees.id = accounts.sales_person"),
+			wantSQL: "UPDATE employees SET sales_count = sales_count + 1 FROM accounts " +
+				"WHERE accounts.name = $1 " +
+				"AND employees.id = accounts.sales_person",
+			wantArgs: []any{"Acme Corporation"},
+		},
+		{
+			name: "from_select",
+			b: Update("employees").Set("sales_count", Expr("sales_count + 1")).FromSelect(
+				Select("name").From("accounts"), "acc",
+			).
+				Where("acc.name = ?", "Acme Corporation").
+				Where("employees.id = acc.sales_person"),
+			wantSQL: "UPDATE employees SET sales_count = sales_count + 1 " +
+				"FROM (SELECT name FROM accounts) " +
+				"AS acc WHERE acc.name = $1 AND employees.id = acc.sales_person",
+			wantArgs: []any{"Acme Corporation"},
+		},
 	}
 
 	for _, tc := range testCases {