H2 SQL数据库-如果记录不存在，则插入 [英] H2 SQL database - INSERT if the record does not exist

问题描述

我想初始化一个H2数据库，但是不确定记录是否存在.如果它们不存在，我什么都不愿做，但是如果它们不存在，我想写默认值.

I would like initialize a H2 database, but I am not sure if the records exist. If they exist I don't want to do anything, but if they don't exist I would like to write the default values.

类似这样的东西:

IF 'number of rows in ACCESSLEVELS' = 0
INSERT INTO ACCESSLEVELS VALUES
    (0, 'admin'),
    (1, 'SEO'),
    (2, 'sales director'),
    (3, 'manager'),
    (4, 'REP')
    ;

推荐答案

以下内容适用于MySQL，PostgreSQL和H2数据库:

The following works for MySQL, PostgreSQL, and the H2 database:

drop table ACCESSLEVELS;

create table ACCESSLEVELS(id int, name varchar(255));

insert into ACCESSLEVELS select * from (
select 0, 'admin' union
select 1, 'SEO' union
select 2, 'sales director' union
select 3, 'manager' union
select 4, 'REP'
) x where not exists(select * from ACCESSLEVELS);

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