使用 ARRAY
在 PostgreSQL 中使用函数处理数据
Brian Piccolo
Sr. Director, Digital Strategy
开始之前
CREATE TABLE 示例
CREATE TABLE my_first_table (
first_column text,
second_column integer
);
INSERT 示例
INSERT INTO my_first_table
(first_column, second_column) VALUES ('text value', 12);
ARRAY：一种特殊类型
让我们创建一个包含两个数组列的简单表。
CREATE TABLE grades (
student_id int,
email text[][],
test_scores int[]
);
带 ARRAY 的 INSERT 语句
示例 INSERT 语句：
INSERT INTO grades
VALUES (1,
'{{"work","[email protected]"},{"other","[email protected]"}}',
'{92,85,96,88}' );
访问 ARRAY
SELECT
email[1][1] AS type,
email[1][2] AS address,
test_scores[1],
FROM grades;
+--------+--------------------+-------------+
| type | address | test_scores |
|--------|--------------------|-------------|
| work | [email protected] | 92 |
| work | [email protected] | 76 |
+--------+--------------------+-------------+
注意：PostgreSQL 的数组下标从 1 开始，而非 0。
搜索 ARRAY
SELECT
email[1][1] as type,
email[1][2] as address,
test_scores[1]
FROM grades
WHERE email[1][1] = 'work';
+--------+--------------------+-------------+
| type | address | test_scores |
|--------|--------------------|-------------|
| work | [email protected] | 92 |
| work | [email protected] | 76 |
+--------+--------------------+-------------+
ARRAY 的函数与运算符
SELECT
email[2][1] as type,
email[2][2] as address,
test_scores[1]
FROM grades
WHERE 'other' = ANY (email);
+---------+---------------------+-------------+
| type | address | test_scores |
|---------|-----------------------------------|
| other | [email protected] | 92 |
| null | null | 76 |
+---------+---------------------+-------------+
ARRAY 的函数与运算符
SELECT
email[2][1] as type,
email[2][2] as address,
test_scores[1]
FROM grades
WHERE email @> ARRAY['other'];
+---------+---------------------+-------------+
| type | address | test_scores |
|---------|-----------------------------------|
| other | [email protected] | 92 |
| null | null | 76 |
+---------+---------------------+-------------+
Passons à la pratique !
在 PostgreSQL 中使用函数处理数据
