如何在PostgreSql(11版)中使用IF语句?我只尝试了原始 IF 用法,但遇到了问题(“IF”处或附近的语法错误)。为了解决这个问题,人们建议使用“do &&”,但效果不佳(Unterminated dollar quote started at position 3 in SQL DO $$ BEGIN IF ......)。这是我的 SQL 代码:
DO $$
BEGIN
IF (NOT EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = 'categories')) THEN
CREATE TABLE IF NOT EXISTS categories
(
id SERIAL NOT NULL,
name character varying(40),
CONSTRAINT categories_pkey PRIMARY KEY (id)
);
INSERT INTO categories (name) VALUES ('Games');
INSERT INTO categories (name) VALUES ('Multimedia');
INSERT INTO categories (name) VALUES ('Productivity');
INSERT INTO categories (name) VALUES ('Tools');
INSERT INTO categories (name) VALUES ('Health');
INSERT INTO categories (name) VALUES ('Lifestyle');
INSERT INTO categories (name) VALUES ('Other');
END IF;
END
$$;
如果表不存在,我只需要创建表并向其中插入一些初始化数据。
最佳答案
一些平台不支持美元报价。在您的具体示例中,您应该在最后一个 END
之后有一个分号。您可能还需要添加一个 DECLARE
语句。
DO
$$
DECLARE
BEGIN
IF (NOT EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = 'categories'))
THEN
CREATE TABLE IF NOT EXISTS categories
(
id SERIAL NOT NULL,
name character varying(40),
CONSTRAINT categories_pkey PRIMARY KEY (id)
);
INSERT INTO categories (name) VALUES ('Games');
INSERT INTO categories (name) VALUES ('Multimedia');
INSERT INTO categories (name) VALUES ('Productivity');
INSERT INTO categories (name) VALUES ('Tools');
INSERT INTO categories (name) VALUES ('Health');
INSERT INTO categories (name) VALUES ('Lifestyle');
INSERT INTO categories (name) VALUES ('Other');
END IF;
END;
$$ LANGUAGE PLPGSQL;
对于不识别美元报价的平台,您可以使用 '
代替。不过,您需要转义匿名函数主体中的任何 '
。
像这样:
DO
'
DECLARE
BEGIN
IF (NOT EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = ''categories''))
THEN
CREATE TABLE IF NOT EXISTS categories
(
id SERIAL NOT NULL,
name character varying(40),
CONSTRAINT categories_pkey PRIMARY KEY (id)
);
INSERT INTO categories (name) VALUES (''Games'');
INSERT INTO categories (name) VALUES (''Multimedia'');
INSERT INTO categories (name) VALUES (''Productivity'');
INSERT INTO categories (name) VALUES (''Tools'');
INSERT INTO categories (name) VALUES (''Health'');
INSERT INTO categories (name) VALUES (''Lifestyle'');
INSERT INTO categories (name) VALUES (''Other'');
END IF;
END;
' LANGUAGE PLPGSQL;
DBFiddle查看工作示例。
关于sql - 未终止美元报价,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/55596620/