# 步骤1：了解SQL关键字
— 查看PostgreSQL保留关键字
SELECT word FROM pg_get_keywords() WHERE catcode = ‘R’ ORDER BY word;

— 查看PostgreSQL非保留关键字
SELECT word FROM pg_get_keywords() WHERE catcode = ‘U’ ORDER BY word;

# 步骤2：制定命名规范
— 制定数据库对象命名规范
– 表名：使用fgedu_前缀，蛇形命名法
– 列名：使用蛇形命名法，避免使用关键字
– 索引名：使用idx_前缀，表名_列名格式
– 函数名：使用fgedu_前缀，蛇形命名法

# 步骤3：创建数据库对象
— 创建表
CREATE TABLE fgedu_fgedus (
id SERIAL PRIMARY KEY,
fgeduname VARCHAR(50) NOT NULL,
email VARCHAR(100) UNIQUE NOT NULL,
created_at TIMESTAMP DEFAULT NOW(),
updated_at TIMESTAMP DEFAULT NOW()
);

— 创建索引
CREATE INDEX idx_fgedu_fgedus_fgeduname ON fgedu_fgedus(fgeduname);
CREATE INDEX idx_fgedu_fgedus_email ON fgedu_fgedus(email);

— 创建函数
CREATE OR REPLACE FUNCTION fgedu_get_fgedu_count()
RETURNS INTEGER AS $$
BEGIN
RETURN (SELECT COUNT(*) FROM fgedu_fgedus);
END;
$$ LANGUAGE plpgsql;

# 步骤4：测试SQL关键字使用
— 执行SQL语句
SELECT * FROM fgedu_fgedus;
INSERT INTO fgedu_fgedus (fgeduname, email) VALUES (‘test’, ‘test@fgedu.net.cn’);
UPDATE fgedu_fgedus SET email = ‘fgfgfgfgtest1@fgedu.net.cn’ WHERE id = 1;
DELETE FROM fgedu_fgedus WHERE id = 1;

# 步骤5：检查命名规范
— 检查表名
SELECT table_name FROM information_schema.tables WHERE table_schema = ‘public’;

— 检查列名
SELECT column_name FROM information_schema.columns WHERE table_schema = ‘public’ AND table_name = ‘fgedu_fgedus’;

# 步骤1：编写SQL语句
— 选择数据
SELECT id, fgeduname, email FROM fgedu_fgedus WHERE fgeduname LIKE ‘test%’;

— 插入数据
INSERT INTO fgedu_fgedus (fgeduname, email) VALUES (‘fgfgfgtest1’, ‘fgfgfgfgtest1@fgedu.net.cn’);

— 更新数据
UPDATE fgedu_fgedus SET email = ‘fgfgfgfgtest1@fgedu.net.cn’ WHERE id = 1;

— 删除数据
DELETE FROM fgedu_fgedus WHERE id = 1;

# 步骤2：使用高级SQL关键字
— 连接查询
SELECT u.fgeduname, o.amount, o.order_date
FROM fgedu_fgedus u
JOIN fgedu_orders o ON u.id = o.fgedu_id
WHERE o.amount > 100
ORDER BY o.order_date DESC;

— 聚合查询
SELECT u.fgeduname, COUNT(*) as order_count, SUM(o.amount) as total_amount
FROM fgedu_fgedus u
JOIN fgedu_orders o ON u.id = o.fgedu_id
GROUP BY u.fgeduname
HAVING COUNT(*) > 5
ORDER BY total_amount DESC;

— 子查询
SELECT * FROM fgedu_fgedus
WHERE id IN (SELECT fgedu_id FROM fgedu_orders WHERE amount > 100);

— 窗口函数
SELECT u.fgeduname, o.amount, o.order_date,
ROW_NUMBER() OVER (PARTITION BY u.id ORDER BY o.order_date) as row_num,
SUM(o.amount) OVER (PARTITION BY u.id) as fgedu_total
FROM fgedu_fgedus u
JOIN fgedu_orders o ON u.id = o.fgedu_id;

# 步骤3：使用特殊SQL关键字
— 使用CTE（Common Table Expression）
WITH fgedu_orders AS (
SELECT fgedu_id, COUNT(*) as order_count, SUM(amount) as total_amount
FROM fgedu_orders
GROUP BY fgedu_id
)
SELECT u.fgeduname, o.order_count, o.total_amount
FROM fgedu_fgedus u
JOIN fgedu_orders o ON u.id = o.fgedu_id
ORDER BY o.total_amount DESC;

— 使用MERGE语句（PostgreSQL 15+）
MERGE INTO fgedu_fgedus u
USING (VALUES (1, ‘test’, ‘test@fgedu.net.cn’)) AS s(id, fgeduname, email)
ON u.id = s.id
WHEN MATCHED THEN
UPDATE SET fgeduname = s.fgeduname, email = s.email
WHEN NOT MATCHED THEN
INSERT (id, fgeduname, email) VALUES (s.id, s.fgeduname, s.email);

# 策略1：命名策略
– 避免使用SQL关键字作为标识符
– 使用有意义的标识符名称
– 采用一致的命名风格

# 策略2：SQL语句编写策略
– 使用大写字母书写关键字
– 适当缩进和换行
– 避免过长的SQL语句

# 策略3：性能优化策略
– 合理使用关键字，避免不必要的操作
– 使用索引相关的关键字
– 优化查询条件

# 策略4：兼容性策略
– 尽量使用标准SQL关键字
– 避免使用PostgreSQL特有的关键字
– 注意不同版本的关键字差异

# 策略5：安全性策略
– 使用参数化查询，避免SQL注入
– 限制用户权限，避免恶意SQL操作
– 审计SQL语句执行

# 示例：SQL关键字使用策略

# 1. 命名策略
— 好的命名
CREATE TABLE fgedu_customers (
customer_id SERIAL PRIMARY KEY,
customer_name VARCHAR(100) NOT NULL,
email_address VARCHAR(100) UNIQUE NOT NULL
);

# 2. SQL语句编写策略
— 好的SQL语句
SELECT
c.customer_id,
c.customer_name,
c.email_address,
COUNT(o.order_id) as order_count,
SUM(o.amount) as total_amount
FROM
fgedu_customers c
LEFT JOIN
fgedu_orders o ON c.customer_id = o.customer_id
GROUP BY
c.customer_id,
c.customer_name,
c.email_address
HAVING
COUNT(o.order_id) > 0
ORDER BY
total_amount DESC
LIMIT 10;

# 3. 性能优化策略
— 优化查询
CREATE INDEX idx_fgedu_orders_customer_amount ON fgedu_orders(customer_id, amount);

SELECT
c.customer_id,
c.customer_name,
SUM(o.amount) as total_amount
FROM
fgedu_customers c
JOIN
fgedu_orders o ON c.customer_id = o.customer_id
WHERE
o.amount > 100
GROUP BY
c.customer_id,
c.customer_name
ORDER BY
total_amount DESC;

# 4. 兼容性策略
— 使用标准SQL
SELECT * FROM fgedu_customers WHERE customer_id = 1;

# 5. 安全性策略
— 使用参数化查询
PREPARE get_customer (INTEGER) AS
SELECT * FROM fgedu_customers WHERE customer_id = $1;

EXECUTE get_customer(1);

# 调优步骤
1. 分析SQL语句性能
2. 优化SQL关键字使用
3. 调整查询结构
4. 测试性能改进

# 调优建议
– 合理使用JOIN关键字，避免不必要的连接
– 使用索引相关的关键字，如USING INDEX
– 优化WHERE子句，使用合适的条件关键字
– 合理使用聚合函数关键字
– 避免使用SELECT *，只选择需要的列

# 示例：SQL关键字性能调优

# 1. 分析SQL语句性能
EXPLAIN ANALYZE
SELECT *
FROM fgedu_customers c
JOIN fgedu_orders o ON c.customer_id = o.customer_id
WHERE o.amount > 100
ORDER BY o.order_date DESC;

# 2. 优化SQL关键字使用
— 优化前
SELECT *
FROM fgedu_customers c
JOIN fgedu_orders o ON c.customer_id = o.customer_id
WHERE o.amount > 100
ORDER BY o.order_date DESC;

— 优化后
SELECT c.customer_id, c.customer_name, o.order_id, o.amount, o.order_date
FROM fgedu_customers c
JOIN fgedu_orders o ON c.customer_id = o.customer_id
WHERE o.amount > 100
ORDER BY o.order_date DESC;

# 3. 调整查询结构
— 优化前
SELECT *
FROM fgedu_orders
WHERE order_date BETWEEN ‘2026-01-01’ AND ‘2026-01-31’;

— 优化后
SELECT *
FROM fgedu_orders
WHERE order_date >= ‘2026-01-01’ AND order_date < '2026-02-01'; # 4. 测试性能改进 -- 插入测试数据 INSERT INTO fgedu_orders (customer_id, amount, order_date) SELECT 1, 100 + generate_series(1, 1000), '2026-01-01'::DATE + generate_series(0, 999); -- 测试查询性能 time psql -U fgedu -d fgedudb -c "SELECT * FROM fgedu_orders WHERE order_date >= ‘2026-01-01’ AND order_date < '2026-02-01';" -- 创建索引后测试 CREATE INDEX idx_fgedu_orders_order_date ON fgedu_orders(order_date); time psql -U fgedu -d fgedudb -c "SELECT * FROM fgedu_orders WHERE order_date >= ‘2026-01-01’ AND order_date < '2026-02-01';"