mysql补上连续日期缺失的天数并把当天数据记为0

可以通过生成一个连续日期序列，然后使用左连接（LEFT JOIN）把日期序列和原始表格连接起来，再使用 IFNULL 函数把空值替换成 0，最后使用 UPDATE 语句更新原始表格。以下是具体的 SQL 代码：

假设原始表格名称为 `my_table`，日期字段名称为 `date_field`，数据字段名称为 `data_field`。

1. 生成连续日期序列

首先，我们需要生成一个连续日期序列。可以使用以下 SQL 语句：

SELECT date_sequence.date
FROM (
  SELECT DATE_SUB(
           DATE(NOW()), INTERVAL n DAY) AS date
  FROM (
    SELECT a.N + b.N * 10 + 1 AS n
    FROM (
      SELECT 0 AS N
      UNION SELECT 1
      UNION SELECT 2
      UNION SELECT 3
      UNION SELECT 4
      UNION SELECT 5
      UNION SELECT 6
      UNION SELECT 7
      UNION SELECT 8
      UNION SELECT 9
    ) AS a
    CROSS JOIN (
      SELECT 0 AS N
      UNION SELECT 1
      UNION SELECT 2
      UNION SELECT 3
      UNION SELECT 4
      UNION SELECT 5
      UNION SELECT 6
      UNION SELECT 7
      UNION SELECT 8
      UNION SELECT 9
    ) AS b
  ) AS numbers
  WHERE DATE_SUB(DATE(NOW()), INTERVAL n DAY) >= '2021-01-01'
) AS date_sequence

这个 SQL 语句可以生成从当前日期往前数 365 天的连续日期序列。如果需要生成更长的日期序列，可以调整 `WHERE` 子句中的日期范围。

2. 连接原始表格和日期序列

接下来，我们使用左连接把原始表格和日期序列连接起来：

SELECT date_sequence.date, my_table.data_field
FROM (
  SELECT date_sequence.date
  FROM (
    SELECT DATE_SUB(
             DATE(NOW()), INTERVAL n DAY) AS date
    FROM (
      SELECT a.N + b.N * 10 + 1 AS n
      FROM (
        SELECT 0 AS N
        UNION SELECT 1
        UNION SELECT 2
        UNION SELECT 3
        UNION SELECT 4
        UNION SELECT 5
        UNION SELECT 6
        UNION SELECT 7
        UNION SELECT 8
        UNION SELECT 9
      ) AS a
      CROSS JOIN (
        SELECT 0 AS N
        UNION SELECT 1
        UNION SELECT 2
        UNION SELECT 3
        UNION SELECT 4
        UNION SELECT 5
        UNION SELECT 6
        UNION SELECT 7
        UNION SELECT 8
        UNION SELECT 9
      ) AS b
    ) AS numbers
    WHERE DATE_SUB(DATE(NOW()), INTERVAL n DAY) >= '2021-01-01'
  ) AS date_sequence
  LEFT JOIN my_table ON date_sequence.date = my_table.date_field
)

这个 SQL 语句会生成一个包含日期序列和原始表格数据的临时表格。

3. 替换空值为 0

现在，我们可以使用 `IFNULL` 函数把空值替换成 0：

SELECT date_sequence.date, IFNULL(my_table.data_field, 0) AS data_field
FROM (
  SELECT date_sequence.date
  FROM (
    SELECT DATE_SUB(
             DATE(NOW()), INTERVAL n DAY) AS date
    FROM (
      SELECT a.N + b.N * 10 + 1 AS n
      FROM (
        SELECT 0 AS N
        UNION SELECT 1
        UNION SELECT 2
        UNION SELECT 3
        UNION SELECT 4
        UNION SELECT 5
        UNION SELECT 6
        UNION SELECT 7
        UNION SELECT 8
        UNION SELECT 9
      ) AS a
      CROSS JOIN (
        SELECT 0 AS N
        UNION SELECT 1
        UNION SELECT 2
        UNION SELECT 3
        UNION SELECT 4
        UNION SELECT 5
        UNION SELECT 6
        UNION SELECT 7
        UNION SELECT 8
        UNION SELECT 9
      ) AS b
    ) AS numbers
    WHERE DATE_SUB(DATE(NOW()), INTERVAL n DAY) >= '2021-01-01'
  ) AS date_sequence
  LEFT JOIN my_table ON date_sequence.date = my_table.date_field
) AS temp_table

这个 SQL 语句会生成一个包含日期序列和数据字段的临时表格，其中缺失的日期对应的数据字段值会被替换成 0。

4. 更新原始表格

最后，我们使用 `UPDATE` 语句更新原始表格：

UPDATE my_table
INNER JOIN (
  SELECT date_sequence.date, IFNULL(my_table.data_field, 0) AS data_field
  FROM (
    SELECT date_sequence.date
    FROM (
      SELECT DATE_SUB(
               DATE(NOW()), INTERVAL n DAY) AS date
      FROM (
        SELECT a.N + b.N * 10 + 1 AS n
        FROM (
          SELECT 0 AS N
          UNION SELECT 1
          UNION SELECT 2
          UNION SELECT 3
          UNION SELECT 4
          UNION SELECT 5
          UNION SELECT 6
          UNION SELECT 7
          UNION SELECT 8
          UNION SELECT 9
        ) AS a
        CROSS JOIN (
          SELECT 0 AS N
          UNION SELECT 1
          UNION SELECT 2
          UNION SELECT 3
          UNION SELECT 4
          UNION SELECT 5
          UNION SELECT 6
          UNION SELECT 7
          UNION SELECT 8
          UNION SELECT 9
        ) AS b
      ) AS numbers
      WHERE DATE_SUB(DATE(NOW()), INTERVAL n DAY) >= '2021-01-01'
    ) AS date_sequence
    LEFT JOIN my_table ON date_sequence.date = my_table.date_field
  ) AS temp_table
) AS new_data
ON my_table.date_field = new_data.date
SET my_table.data_field = new_data.data_field;

这个 SQL 语句会使用临时表格中的数据更新原始表格中的数据。注意，这个 SQL 语句只会更新日期序列中存在的日期对应的数据字段，日期序列中缺失的日期对应的数据字段值不会被更新。如果需要更新所有日期对应的数据字段值，可以在第三步中使用 `COALESCE` 函数把空值替换成 0。