数据操作语言（DML）语句

BigQuery 入门

Matt Forrest

Field CTO

BigQuery 中的数据操作概览

INSERT：添加新行。
UPDATE：修改现有行中的值。
DELETE：从表中删除不需要的数据。
MERGE：将 INSERT、UPDATE、DELETE 合并为一条语句。
CREATE TABLE AS：根据查询结果创建新表。

注意事项与性能

尽量将 DML 语句批量执行，而非逐条运行
运行 UPDATE 时必须包含 WHERE 条件
考虑使用分区和聚簇表

¹ https://cloud.google.com/bigquery/docs/reference/standard-sql/data-manipulation-language

INSERT

向表添加记录

-- Define the columns in the parentheses 
INSERT INTO customers (customer_id, name, email)

-- Each value is a row to be inserted
VALUES (1, "John Doe", "[email protected]"),
(2, "Jane Doe", "[email protected]"),
(3, "Alice Smith", "[email protected]");

UPDATE

基于条件修改数据

UPDATE customers
-- Set one column for each SET statement
SET email = "[email protected]"
-- Make sure to include where otherwise all
-- rows will be updated
WHERE customer_id = 1;

将 UPDATE 与子查询或连接一起使用

UPDATE customers c
SET c.email = e.email
FROM emails e
WHERE c.customer_id = 1;

DELETE

DELETE 会永久删除记录，且不可撤销

DELETE FROM customers

-- Include WHERE to ensure only specific rows are deleted
WHERE customer_id = 3;

DELETE FROM customers c
JOIN emails e USING (customer_id)
WHERE email = '[email protected]'

MERGE

在一次操作中组合 INSERT、UPDATE 和 DELETE

-- Sets the customers table as the target
MERGE customers AS target

-- The source is set to new_customers
USING new_customers AS source

-- Matching condition
ON target.customer_id = source.customer_id

-- If the emails do not match, update the email
WHEN MATCHED AND target.email != source.email THEN
  UPDATE SET email = source.email

-- If the match is not met, insert the record
WHEN NOT MATCHED THEN
  INSERT (customer_id, name, email) VALUES 
  (source.customer_id, source.name, source.email);

CREATE TABLE

通过查询创建新表

CREATE TABLE active_customers AS
SELECT customer_id, name, email 
FROM customers
WHERE last_active_date > DATE_SUB(CURRENT_DATE(), INTERVAL 30 DAY);

Vamos praticar!

BigQuery 入门