no zuo no die系列，来自于pg的wiki。 这一节的内容是：不要使用money。 理由是: >money It's a fixed-point type, implemented as a machine int, so arithmetic with it is fast. But it doesn't handle fractions of a cent (or equivalents in other currencies), it's rounding behaviour is probably not what you want. It doesn't store a currency with the value, rather assuming that all money columns contain the currency specified by the database's lc_monetary locale setting. If you change the lc_monetary setting for any reason, all money columns will contain the wrong value. That means that if you insert '$10.00' while lc_monetary is set to 'en_US.UTF-8' the value you retrieve may be '10,00 Lei' or '¥1,000' if lc_monetary is changed. Storing a value as a numeric, possibly with the currency being used in an adjacent column, might be better. 原因是money类型是定点类型，在计算机中通过机器int类型实现，取整行为可能不符合期望，同时该字段并没有存储货币单位，取决于数据库的lc_monetary设定，如果计量单位变化那么该值可能会存在问题，因此使用numeric存储数值额外使用其他字段存储货币单位。 ``` [local]:5432 pg12@testdb=# drop table if exists t_money; NOTICE: table "t_money" does not exist, skipping DROP TABLE Time: 35.404 ms [local]:5432 pg12@testdb=# create table t_money(id int,c1 money); CREATE TABLE Time: 133.600 ms [local]:5432 pg12@testdb=# insert into t_money(id,c1) values(1,112343.01); INSERT 0 1 Time: 0.929 ms [local]:5432 pg12@testdb=# insert into t_money(id,c1) values(2,112343.31234); INSERT 0 1 Time: 0.640 ms [local]:5432 pg12@testdb=# insert into t_money(id,c1) values(3,112343.50); INSERT 0 1 Time: 0.599 ms [local]:5432 pg12@testdb=# insert into t_money(id,c1) values(4,112343.99); INSERT 0 1 Time: 0.523 ms [local]:5432 pg12@testdb=# insert into t_money(id,c1) values(5,112343.3199); INSERT 0 1 Time: 0.483 ms [local]:5432 pg12@testdb=# insert into t_money(id,c1) values(6,112343.3150); INSERT 0 1 Time: 0.533 ms [local]:5432 pg12@testdb=# insert into t_money(id,c1) values(7,112343.3101); INSERT 0 1 Time: 0.531 ms [local]:5432 pg12@testdb=# ``` 查询数据，实际的数据是四舍五入，保留两位小数 ``` [local]:5432 pg12@testdb=# select * from t_money; id | c1 ----+------------- 1 | $112,343.01 2 | $112,343.31 3 | $112,343.50 4 | $112,343.99 5 | $112,343.32 6 | $112,343.32 7 | $112,343.31 (7 rows) Time: 0.321 ms ``` 修改数据库参数的货币设置为zh_CN ``` [local]:5432 pg12@testdb=# [local]:5432 pg12@testdb=# show lc_monetary; lc_monetary ------------- zh_CN.UTF-8 (1 row) Time: 5.212 ms [local]:5432 pg12@testdb=# select * from t_money; id | c1 ----+-------------- 1 | ￥112,343.01 2 | ￥112,343.31 3 | ￥112,343.50 4 | ￥112,343.99 5 | ￥112,343.32 6 | ￥112,343.32 7 | ￥112,343.31 (7 rows) Time: 2.092 ms [local]:5432 pg12@testdb=# ``` 美钞成了人民币。 **参考资料** [Don't Do This](https://wiki.postgresql.org/wiki/Don't_Do_This)