In MySQL, the REPLACE() function can replace the string in the field. The syntax is UPDATE table name. SET field name = REPLACE(field name, 'old content', 'new content'); 1. This operation is replaced globally and case-sensitive; 2. It is recommended to perform backup or add WHERE conditional tests; 3. The replacement effect can be previewed in SELECT; 4. Pay attention to avoiding error substitution, performance impact and data backup problems.
In MySQL, if you want to search for strings in a field and replace some content, the most common method is to use the REPLACE() function. This function can help you quickly update the values ??of certain fields in the table, such as fixing error data, unified format, etc.
How to use the REPLACE() function
MySQL's REPLACE(str, from_str, to_str) function replaces all from_str in the string str to_str . It's very straightforward and the syntax is simple:
UPDATE table name SET Field name = REPLACE(field name, 'the content to be replaced', 'the content to be replaced');
For example, suppose you have an article table articles with a content field inside. You want to replace the " http://miracleart.cn/link/658900b7144ee7b4f419cb8054361045 " in all articles with " http://miracleart.cn/link/80b912d8d81919969ccab0080ddd8e2f :
UPDATE articles SET content = REPLACE(content, 'http://miracleart.cn/link/658900b7144ee7b4f419cb8054361045', 'https://example.com');
What should be noted is:
- This operation is a global replacement , which means that all matching parts in the field will be replaced
- It is case-sensitive (unless your fields are case-insensitive sorting rules)
- Once executed, the data will be modified. It is recommended to back up or add
WHEREconditions to test it.
Do search and replace when querying without modifying the original data
If you just want to see the replacement in the query result and don't really want to change the content in the database, you can also use REPLACE() in the SELECT statement:
SELECT id, REPLACE(content, 'old content', 'new content') AS new_content FROM articles;
In this way, you can preview the replacement effect and confirm that there is no problem before deciding whether to execute UPDATE .
Notes and FAQs
Don't forget to add WHERE condition : If you only want to replace specific records, remember to add the
WHEREclause, otherwise the data of the entire table will be updated.UPDATE articles SET content = REPLACE(content, 'old-text', 'new-text') WHERE id = 100;
Avoid misreplacement : If the replaced content appears where you do not want it, such as "old-text" appears in the middle of other words, it may also be replaced. This situation may require more complex logic, such as incorporating regular expressions (MySQL 8.0 supports
REGEXP_REPLACE()).Performance Impact : Performing full-field replacement for large tables may be slower, especially fields without indexes. It is recommended to operate during the low peak period or process in batches.
Backup is very important : it is best to export relevant data before execution to prevent data loss due to replacement errors.
Basically that's it. Mastering REPLACE() and REGEXP_REPLACE() will be much more convenient for daily maintenance or data cleaning.
The above is the detailed content of mysql find and replace in string. For more information, please follow other related articles on the PHP Chinese website!
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