检查Tarantool中是否存在SQL表

Question

如何在Tarantool SQL中检查表是否已存在？

- Elena Shebunyaeva

Answer 1

只使用 SQL 设施，可以这样做：

SELECT EXISTS (select true from "_space" where "name" = 'table_name')

例如：

tarantool> SELECT EXISTS (select true from "_space" where "name" = 'T1')
---
- metadata:
  - name: EXISTS (select true from "_space" where "name" = 'T1')
    type: boolean
  rows:
  - [true]
...

tarantool> SELECT EXISTS (select true from "_space" where "name" = 'T')
---
- metadata:
  - name: EXISTS (select true from "_space" where "name" = 'T')
    type: boolean
  rows:
  - [false]
...

在Lua模式下：

tarantool> box.space.T1 ~= nil
---
- true
...

tarantool> box.space.T ~= nil
---
- false
...

- NikitaRock

---

与nil进行比较只有在您明确想要布尔类型或想要特别表达检查存在意图时才是必要的。否则，您可以只需执行if box.space.T1 then print 'yes' else print 'no' end或print(box.space.T1 and 'yes' or 'no') :D - DarkWiiPlayer