SQL一键拆列，轻松搞定数据难题

2023-08-15 18:11:57

使用 SQL 轻松拆分列

在数据处理中，经常需要将一列数据拆分成多列，例如地址信息、多值列表等。SQL 提供了多种方法来实现列拆分，本文将深入探讨其中一些常用的技巧。

1. 使用字符串函数拆分列

字符串函数是拆分列最简单的方法之一。SUBSTRING()、LEFT() 和 RIGHT() 等函数可用于提取列中的特定字符或字符串。

SELECT
  SUBSTRING(address, 1, INSTR(address, ',') - 1) AS street_address,
  SUBSTRING(address, INSTR(address, ',') + 2, INSTR(address, ',') - INSTR(address, ',')) AS city,
  SUBSTRING(address, INSTR(address, ',') + INSTR(address, ',') + 3, 2) AS state,
  SUBSTRING(address, INSTR(address, ',') + INSTR(address, ',') + 6) AS zip_code
FROM table_name;

2. 使用正则表达式拆分列

正则表达式是用于提取和匹配字符串中特定模式的强大工具。它们可用于拆分列并存储结果到新列中。

SELECT
  REGEXP_SUBSTR(address, '^(.*?), (.*?), ([A-Z]{2}) ([0-9]{5})SELECT
  REGEXP_SUBSTR(address, '^(.*?), (.*?), ([A-Z]{2}) ([0-9]{5})$', 1) AS street_address,
  REGEXP_SUBSTR(address, '^(.*?), (.*?), ([A-Z]{2}) ([0-9]{5})$', 2) AS city,
  REGEXP_SUBSTR(address, '^(.*?), (.*?), ([A-Z]{2}) ([0-9]{5})$', 3) AS state,
  REGEXP_SUBSTR(address, '^(.*?), (.*?), ([A-Z]{2}) ([0-9]{5})$', 4) AS zip_code
FROM table_name;
#x27;, 1) AS street_address,
  REGEXP_SUBSTR(address, '^(.*?), (.*?), ([A-Z]{2}) ([0-9]{5})SELECT
  REGEXP_SUBSTR(address, '^(.*?), (.*?), ([A-Z]{2}) ([0-9]{5})$', 1) AS street_address,
  REGEXP_SUBSTR(address, '^(.*?), (.*?), ([A-Z]{2}) ([0-9]{5})$', 2) AS city,
  REGEXP_SUBSTR(address, '^(.*?), (.*?), ([A-Z]{2}) ([0-9]{5})$', 3) AS state,
  REGEXP_SUBSTR(address, '^(.*?), (.*?), ([A-Z]{2}) ([0-9]{5})$', 4) AS zip_code
FROM table_name;
#x27;, 2) AS city,
  REGEXP_SUBSTR(address, '^(.*?), (.*?), ([A-Z]{2}) ([0-9]{5})SELECT
  REGEXP_SUBSTR(address, '^(.*?), (.*?), ([A-Z]{2}) ([0-9]{5})$', 1) AS street_address,
  REGEXP_SUBSTR(address, '^(.*?), (.*?), ([A-Z]{2}) ([0-9]{5})$', 2) AS city,
  REGEXP_SUBSTR(address, '^(.*?), (.*?), ([A-Z]{2}) ([0-9]{5})$', 3) AS state,
  REGEXP_SUBSTR(address, '^(.*?), (.*?), ([A-Z]{2}) ([0-9]{5})$', 4) AS zip_code
FROM table_name;
#x27;, 3) AS state,
  REGEXP_SUBSTR(address, '^(.*?), (.*?), ([A-Z]{2}) ([0-9]{5})SELECT
  REGEXP_SUBSTR(address, '^(.*?), (.*?), ([A-Z]{2}) ([0-9]{5})$', 1) AS street_address,
  REGEXP_SUBSTR(address, '^(.*?), (.*?), ([A-Z]{2}) ([0-9]{5})$', 2) AS city,
  REGEXP_SUBSTR(address, '^(.*?), (.*?), ([A-Z]{2}) ([0-9]{5})$', 3) AS state,
  REGEXP_SUBSTR(address, '^(.*?), (.*?), ([A-Z]{2}) ([0-9]{5})$', 4) AS zip_code
FROM table_name;
#x27;, 4) AS zip_code
FROM table_name;

3. 使用临时表拆分列

临时表是创建在内存中的临时表，可用于 SQL 查询中。它可用于拆分列并将结果存储到新的临时表中。

CREATE TEMP TABLE address_parts (
  street_address VARCHAR(255),
  city VARCHAR(255),
  state VARCHAR(2),
  zip_code VARCHAR(10)
);

INSERT INTO address_parts (
  street_address,
  city,
  state,
  zip_code
)
SELECT
  SUBSTRING(address, 1, INSTR(address, ',') - 1),
  SUBSTRING(address, INSTR(address, ',') + 2, INSTR(address, ',') - INSTR(address, ',')) AS city,
  SUBSTRING(address, INSTR(address, ',') + INSTR(address, ',') + 3, 2) AS state,
  SUBSTRING(address, INSTR(address, ',') + INSTR(address, ',') + 6) AS zip_code
FROM table_name;

SELECT * FROM address_parts;