计算机二级VFP知识点SQL命令

该大纲涵盖了计算机二级VFP知识点中的SQL命令，包括SELECT、INSERT、UPDATE、DELETE、JOIN、WHERE、ORDER BY、GROUP BY、HAVING和DISTINCT。 这些命令分别涉及查询、插入、更新、删除、连接、条件筛选、排序、分组和去重等功能。 通过学习这些知识点，学习者可以掌握SQL的基本操作和数据处理技巧。

计算机二级VFP知识点SQL命令

• 示例：SELECT * FROM table_name
  • 示例：SELECT column1, column2 FROM table_name
    • 示例：SELECT column1, column2 FROM table_name WHERE condition
    • 示例：SELECT column1, column2 FROM table_name ORDER BY column1 DESC
  • 示例：SELECT COUNT(column_name) FROM table_name
• 示例：SELECT column1, AVG(column2) FROM table_name GROUP BY column1
• INSERT命令
  • 示例：INSERT INTO table_name VALUES (value1, value2)
    • 示例：INSERT INTO table_name (column1, column2) VALUES (value1, value2)
      • 示例：INSERT INTO table_name (column1, column2) SELECT column1, column2 FROM table_name2
  • 示例：INSERT INTO table_name SELECT * FROM table_name2 WHERE condition
• UPDATE命令
  • 示例：UPDATE table_name SET column1 = value1, column2 = value2 WHERE condition
    • 示例：UPDATE table_name SET column1 = value1, column2 = value2
      • 示例：UPDATE table_name SET column1 = column1 + 1 WHERE condition
  • 示例：UPDATE table_name SET column1 = (SELECT column2 FROM table_name2 WHERE condition) WHERE condition
• DELETE命令
  • 示例：DELETE FROM table_name WHERE condition
    • 示例：DELETE FROM table_name
      • 示例：DELETE FROM table_name WHERE column1 IN (SELECT column1 FROM table_name2 WHERE condition)
  • 示例：DELETE FROM table_name1 WHERE column1 IN (SELECT column1 FROM table_name2 WHERE condition)
• JOIN命令
  • 示例：SELECT * FROM table_name1 JOIN table_name2 ON table_name1.column1 = table_name2.column1
    • 示例：SELECT column1, column2 FROM table_name1 INNER JOIN table_name2 ON table_name1.column1 = table_name2.column1
      • 示例：SELECT * FROM table_name1 LEFT JOIN table_name2 ON table_name1.column1 = table_name2.column1
  • 示例：SELECT * FROM table_name1 RIGHT JOIN table_name2 ON table_name1.column1 = table_name2.column1
• WHERE命令
  • 示例：SELECT * FROM table_name WHERE condition
    • 示例：SELECT * FROM table_name WHERE column1 IN (value1, value2)
      • 示例：SELECT * FROM table_name WHERE column1 BETWEEN value1 AND value2
  • 示例：SELECT * FROM table_name WHERE EXISTS (SELECT * FROM table_name2 WHERE condition)
• ORDER BY命令
  • 示例：SELECT * FROM table_name ORDER BY column1 ASC
    • 示例：SELECT * FROM table_name ORDER BY column1 DESC
• GROUP BY命令
  • 示例：SELECT column1, COUNT(*) FROM table_name GROUP BY column1
    • 示例：SELECT column1, AVG(column2) FROM table_name GROUP BY column1
• HAVING命令
  • 示例：SELECT column1, COUNT(*) FROM table_name GROUP BY column1 HAVING COUNT(*) > 1
    • 示例：SELECT column1, AVG(column2) FROM table_name GROUP BY column1 HAVING AVG(column2) > 50
• DISTINCT命令
  • 示例：SELECT DISTINCT column1 FROM table_name
    • 示例：SELECT column1, column2 FROM table_name1 JOIN table_name2 ON table_name1.column1 = table_name2.column1