update tablename set source_name = "bj1062-北京市朝阳区常营北辰福第"
where source_name = "-北京市朝阳区常营北辰福第"

update tbl_name set str_col="xxx" = "yyy"

update tbl_name set (str_col="xxx" )= "yyy"

update tbl_name set str_col=("xxx" = "yyy")

select "xxx" = "yyy"

update tbl_name set str_col="xxx" = "yyy"

update tbl_name set str_col=0

mysql [localhost] {msandbox} (test) > select id,str_col from tbl_name where str_col="xxx" = "yyy";
+----+---------+
| id | str_col |
| 1 | aaa |
+----+---------+ | 2 | aaa |
+----+---------+
| 3 | aaa |
| 4 | aaa |

mysql [localhost] {msandbox} (test) > warnings
Show warnings enabled.
mysql [localhost] {msandbox} (test) > explain extended select id,str_col from tbl_name where str_col="xxx" = "yyy"\G
*************************** 1. row ***************************
id: 1 select_type: SIMPLE table: tbl_name type: index
1 row in set, 1 warning (0.00 sec)
possible_keys: NULL
key: idx_str
ref: NULL
key_len: 33 rows: 4
Extra: Using where; Using index
filtered: 100.00
Note (Code 1003): /* select#1 */ select `test`.`tbl_name`.`id` AS `id`,`test`.`tbl_name`.`str_col` AS `str_col` from `test`.`tbl_name` where ((`test`.`tbl_name`.`str_col` = 'xxx') = 'yyy')

((`test`.`tbl_name`.`str_col` = 'xxx') = 'yyy')

mysql [localhost] {msandbox} (test) > select 'yyy'+0.0;
+-----------+
| 'yyy'+0.0 |
| 0 |
+-----------+
mysql [localhost] {msandbox} (test) > select 0=0;
+-----------+
1 row in set, 1 warning (0.00 sec)
+-----+
1 row in set (0.00 sec)
| 0=0 |
+-----+
+-----+
| 1 |

select id,str_col from tbl_name where 1=1;