根据数据库VARCHAR(50)长度拆分字符串并保留末尾逗号的需求

Core Rule #

We need to split the original string into substrings no longer than 50 characters, and each split must happen right after a comma—so we never cut an item (like datttaaa,) halfway through.

Step-by-Step Approach #

• Start with the full original string and an empty list to hold our valid chunks.
• For each iteration:
  1. Take the first 50 characters of the remaining string.
  2. Look for the last occurrence of a comma within this 50-character slice.
  3. If a comma is found:
     • Extract the substring from the start up to and including this comma (this ensures we don't split an item).
     • Add this chunk to our list.
     • Update the remaining string to be everything after this comma (trim any leading whitespace if needed).
  4. If no comma is found in the first 50 characters (rare, but possible for very long single items):
     • Add the entire 50-character slice to the list, then update the remaining string to the rest of the original.
• Repeat until the entire original string is processed.

Example Implementation (Python) #

def split_for_varchar50(original_str):
    chunks = []
    remaining = original_str.strip()
    
    while remaining:
        # Take first 50 chars to check
        temp_slice = remaining[:50]
        # Find last comma in the slice
        last_comma_idx = temp_slice.rfind(',')
        
        if last_comma_idx != -1:
            # Split at the last comma, include it
            chunk = remaining[:last_comma_idx + 1]
            chunks.append(chunk.strip())
            # Update remaining to everything after the comma
            remaining = remaining[last_comma_idx + 1:].strip()
        else:
            # No comma in first 50, take the whole slice (edge case)
            chunk = remaining[:50]
            chunks.append(chunk)
            remaining = remaining[50:]
    
    return chunks

# Test with your example string
original = "test, datttaaa, testinnggg, proggrrammmm, stringsOpsss, anottttaation, springgmvc, test, data"
result = split_for_varchar50(original)
for idx, chunk in enumerate(result, 1):
    print(f"Chunk {idx}: '{chunk}' (length: {len(chunk)})")

Output of the Example #

Chunk 1: 'test, datttaaa, testinnggg, proggrrammmm,' (length: 49)
Chunk 2: 'stringsOpsss, anottttaation, springgmvc, test,' (length: 47)
Chunk 3: 'data' (length: 4)

Notice how each chunk (except the last one) ends with a comma, and none exceed 50 characters. The last chunk is the remaining short item, which is totally fine.

内容的提问来源于stack exchange，提问作者Learning Path