Hey there! That conversion error is super common when working with DateTime columns, especially when mismatches pop up between string inputs and date data types. Let’s walk through the most likely fixes to get your query working:

• Ditch string concatenation for parameterized queries
  If you’re building queries by gluing date strings directly into your SQL (like WHERE DateCol = '05/20/2024 14:30'), you’re not just risking conversion errors—you’re opening the door to SQL injection. Parameterized queries solve both problems. Here’s a quick C# example:

  using (var cmd = new SqlCommand("SELECT * FROM YourTable WHERE DateColumn = @TargetDate", yourConnection))
  {
      cmd.Parameters.Add("@TargetDate", SqlDbType.DateTime).Value = new DateTime(2024, 5, 20, 14, 30, 0);
      // Execute your query here
  }
  

  For raw SQL, use the parameter syntax your database supports (e.g., ? for MySQL, @param for SQL Server).

• Trim milliseconds from the column to match your query value
  If your DateTime column stores milliseconds but you’re searching for values without them, adjust the column value in your query to align:

  • SQL Server:

    -- Strip milliseconds from the column
    SELECT * FROM YourTable
    WHERE DATEADD(ms, -DATEPART(ms, DateColumn), DateColumn) = '2024-05-20 14:30:00'
    -- Or convert to datetime2(0) which automatically removes milliseconds
    SELECT * FROM YourTable
    WHERE CONVERT(datetime2(0), DateColumn) = CONVERT(datetime2(0), '2024-05-20 14:30:00')
    

  • MySQL:

    SELECT * FROM YourTable
    WHERE DATE_FORMAT(DateColumn, '%Y-%m-%d %H:%i:%s') = '2024-05-20 14:30:00'
    

• Double-check your column’s data type
  Make sure the column you’re querying is actually a DateTime-type column (not VARCHAR). If it’s stored as a string, you can convert it temporarily in the query (but fix the schema long-term—always use date-specific types for dates!):

  -- SQL Server example: Convert string column to DateTime (format 120 = yyyy-MM-dd HH:mm:ss)
  SELECT * FROM YourTable
  WHERE CONVERT(datetime, DateColumn, 120) = '2024-05-20 14:30:00'
  

• Hunt for invalid date values
  If your column is a string type, malformed entries could be causing the conversion failure. Find problematic rows with this query:

  -- SQL Server: Identify rows that can't be converted to DateTime
  SELECT DateColumn FROM YourTable
  WHERE TRY_CONVERT(datetime, DateColumn) IS NULL
  

Start with parameterized queries first—they’re the most reliable fix for this kind of error. If you can share a snippet of your actual code/query, I can help refine the solution even more!

内容的提问来源于stack exchange，提问作者Lamis Abouzina