SELECT
语句。假设你有一个名为 employees
的表,你可以使用以下语句来查询表中的所有数据:,,``sql,SELECT * FROM employees;,
``sql,CREATE TEMPORARY TABLE temp_table AS SELECT * FROM original_table WHERE condition;,
``sql,SELECT column_name, COUNT(*),FROM table_name,GROUP BY column_name,HAVING COUNT(*) > 1;,
``,,这段代码会返回在指定列中出现次数超过一次的所有数据。JOIN
子句来查询两个表的数据。,,``sql,SELECT a.column1, b.column2,FROM table1 a,JOIN table2 b ON a.common_column = b.common_column;,
``,,这段 SQL 语句将返回两个表中匹配的记录。sql,SELECT a.column1, b.column2,FROM table1 a,JOIN table2 b ON a.id = b.id;,
``,,这段SQL代码会从table1和table2中查询数据,并将结果合并在一起。GROUP BY
和 HAVING
子句。,,``sql,SELECT column_name, COUNT(*),FROM table_name,GROUP BY column_name,HAVING COUNT(*) > 1;,
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