要计算列中存在的-1和1的数量,可以使用SQL的COUNT
函数结合CASE
语句来实现。以下是一个示例查询:
SELECT
COUNT(CASE WHEN column_name = -1 THEN 1 END) AS count_minus_one,
COUNT(CASE WHEN column_name = 1 THEN 1 END) AS count_one
FROM table_name;
在这个查询中:
table_name
是你要查询的表名。column_name
是你要计算-1和1数量的列名。count_minus_one
和 count_one
是计算结果的别名,分别表示-1和1的数量。CASE
语句可以使查询逻辑更加清晰。如果列中包含NULL
值,COUNT
函数会忽略这些值。如果需要计算包括NULL
在内的所有行数,可以使用IS NULL
条件。
SELECT
COUNT(CASE WHEN column_name = -1 THEN 1 END) AS count_minus_one,
COUNT(CASE WHEN column_name = 1 THEN 1 END) AS count_one,
COUNT(*) AS total_count
FROM table_name;
确保列名和表名拼写正确,否则会报错。
SELECT
COUNT(CASE WHEN wrong_column_name = -1 THEN 1 END) AS count_minus_one,
COUNT(CASE WHEN wrong_column_name = 1 THEN 1 END) AS count_one
FROM wrong_table_name;
确保列的数据类型与查询条件匹配。例如,如果列是字符串类型,需要使用引号包裹值。
SELECT
COUNT(CASE WHEN column_name = '-1' THEN 1 END) AS count_minus_one,
COUNT(CASE WHEN column_name = '1' THEN 1 END) AS count_one
FROM table_name;
希望这些信息对你有所帮助!
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