database - PostgreSql + 将 bool 值类型转换为字符类型

Question

在这里，我无法在 postgre sql 查询中将 bool 值转换为字符。

SELECT *FROM ltl_class_nmfc_aliases 
WHERE ltl_class_nmfc_aliases.id 
NOT IN(SELECT ltl_class_nmfc_aliases_id FROM commodities_shippeds 
WHERE commodities_shipped_obj_type LIKE 'ClientOffice') 
OR ltl_class_id IS NULL 
AND lower(commodity_description_alias) LIKE E'%%' 
AND lower(ltl_value) LIKE E'%92.5%' 
AND hazardous :: integer LIKE E  '%%' 
AND cast(schedule_b as character varying(255)) LIKE E'%%' 
AND cast(harmonized_tariff as character varying(255)) LIKE E'%%' 
ORDER BY commodity_description_alias,ltl_value LIMIT 25;

这里我无法在 AND hazardous::integer LIKE E '%%' 处进行类型转换 建议我如何进行类型转换？

Answer 1

使用 case 语句怎么样？

(case when hazardous then 'Bad juju' else 'Ok.' end) as safety

你也可以使用cast语句:

postgres=# select cast(1 as boolean);
 bool
------
 t

postgres=# select cast(0 as boolean);
 bool
------
 f

postgres=# select cast('false' as boolean);
 bool
------
 f

postgres=# select cast('False' as boolean);
 bool
------
 f

postgres=# select cast('T' as boolean);
 bool
------
 t

postgres=# select cast('F' as boolean);
 bool
------
 f

postgres=# select cast('Y' as boolean);
 bool
------
 t

postgres=# select cast('N' as boolean);
 bool
------
 f

可能是:

 select ... where ... and hazardous = cast(:your_variable as bool)

您也可以转换为 varchar:

select cast(hazardous to varchar)...

一些数据库驱动程序实现(如 Borland 的 BDE)对此感到窒息，因为他们期望 varchar 字段有明确的列宽。

如果您只是过滤 hazardous=true，请仅使用“AND hazardous”。