I recently stumbled across a major character encoding issue on one of the websites I run.
Fixing the problem was a challenge, so I wanted to share some of the knowledge I gained in case anyone else finds similar issues on their own websites. The post below is a long yet detailed account of my experience. I started looking into the issue, and saw the same thing he was. The debug logs from the search page showed the following SQL query being used:. I took the exact same query and ran it in the command-line mysql client. Strangely, this returned a different result:.
You can specify a default character set per MySQL server, database, or table.
Command Line Solution and Exclude Views
The defaults for a database will get applied to new tables, and the defaults for a table will get applied to new columns. The problem was fixed! Or was it? A couple minutes later, I was browsing the site and started coming across funky characters everywhere. These strange character sequences also looked like an issue I had noticed from time to time in phpMyAdmin with edit fields showing strange characters.
Seeing these strange characters sequences everywhere scared me enough to look into the problem a bit more. As you can see, the search term kind-of worked. The column type and character set of a column determine how queries work against the data and how the data is returned as a result of a SELECT query.
It was set to latin1 when the database was created. The problems only occur when you ask MySQL to, on its own, analyze the column or present it. So all this time, my PHP web application had been storing UTFencoded data in the city column, and later retrieving the exact same binary data which it display on the website. For characters abovea multi-byte sequence describes the character. I have over tables in latin1 that should be UTF-8 and need to be converted.
So I started investigating what it takes to convert my existing latin1 tables to UTF-8 as appropriate. Some people have successfully exported their data to latin1, converted the resulting file to UTF-8 via iconv or a similar utility, updated their column definitions, then re-imported that data. Unfortunately this requires taking the database down as tables are dropped and re-created, and this can be a bit time-consuming.
The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. Or if you're still on MySQL 5. Then you need to set the default char sets on the database. This does not convert existing tables, it only sets the default for newly created tables. Then, you will need to convert the char set on all existing tables and their columns.
This assumes that your current data is actually in the current char set. If your columns are set to one char set but your data is really stored in another then you will need to check the MySQL manual on how to handle this.Open source metrology software
Use HeidiSQL. Its free and a very good db tool. The real pitfall when moving from latin to utf8 is to make sure pdo connects with utf8 charset. If not you will get rubbish data inserted to the utf8 table and question marks all over the place on your web page, making you think the table data is not utf If the contents are encoded in a different character set, you can convert the column to use a binary data type first, and then to a nonbinary column with the desired character set.
Make sure to choose the right collation, or you might get unique key conflicts. I had a situation where certain characters "broke" in emails even though they were stored as UTF-8 in the database.
If you are sending emails using utf8 data, you might want to also convert your emails to send in UTF8. For databases that have a high number of tables you can use a simple php script to update the charset of the database and all of the tables using the following:.
The safest way is to modify the columns first to a binary type and then modify it back to it type using the desired charset. If you cannot get your tables to convert or your table is always set to some non-utf8 character set, but you want utf8, your best bet might be to wipe it out and start over again and explicitly specify:.
I am simply completing Jasny's answer for others like Brian and I who have views in our database. It's because you probably have views and you need to exclude them. But when trying to exclude them, MySQL returns 2 columns instead of 1. So we have to adapt Jasny's command with awk to extract only the 1st column which contains the table name. Learn more. Ask Question. Asked 8 years, 10 months ago.
Active 26 days ago. Viewed k times. Nanne Dean Dean 6, 8 8 gold badges 26 26 silver badges 30 30 bronze badges.Glossary of recruitment terms
If you want full UTF-8 support you'll probably also want to use a character set of utf8mb4 rather than utf8 as utf8 only supports the basic multilingual plane as opposed to the full range.
It requires MySQL 5. MartinSteel I believe that's the collation by default with that character set. Active Oldest Votes. BalusC BalusC k gold badges silver badges bronze badges. This rebuilds the table making it infeasible on large production systems. Andrew Large production systems usually have a mirrored DB for maintenance.
The exact statement depends on the column type, maximum length, and other properties. Note, however, that you cannot fully automate the conversion from utf8 to utf8mb4.Shift roster excel
Section I have a solution that will convert databases and tables by running a few commands. It also converts all columns of the type varchartexttinytextmediumtextlongtextchar. You should also backup your database in case something breaks. This will generate a new file alterTables.
Run the following command to start the conversion:. If that happens you can simply change the column to be smaller, like varcharand rerun the command. But you can simply replace this. I used the following shell script.
It takes database name as a parameter and converts all tables to another charset and collation given by another parameters or default value defined in the script. I think but am not sure that Raihan's suggestion only changes the default for the table. First, you need to edit my. Instructions given here. If you get an error like - Specified key was too long; max key length is bytes.
Step 3: then run the alter table query for that table again and table should now be converted into utf8mb4 successfully. For MySQL version 5. For people who might have this problem the best solution is to modify first the columns to a binary type, according to this table:. I made a script which does this more or less automatically:. Sign up to join this community. The best answers are voted up and rise to the top.
Home Questions Tags Users Unanswered. How to easily convert utf8 tables to utf8mb4 in MySQL 5.S9 sprint unlock z3x
Asked 8 years, 4 months ago. Active 9 months ago. Viewed k times. Active Oldest Votes. John aka hot2use When you create a new database on MySQL, the default behaviour is to create a database supporting the latin1 character set. This is fine for most use cases, however if your application needs to support natural languages that do not use the Latin alphabet Greek, Japanese, Arabic etc.
In this tutorial, I will show you have to convert an existing database and tables from latin1 to the utf8 character set. Firstly we are going to create a test database for testing the migration process. Note that if you are going to migrate a real database, you should run this procedure against an offline backup, not against a live production system.
The new database and table will have the latin1 character set by default on a stock MySQL installation, lets confirm this:.
To begin with, we will alter the default character set on the new database to be utf8, which will ensure that any new tables in this database will use this by default:. That takes care of new tables, but for existing tables we have to do something a little more complex. Drop back to your bash terminal, and run the following command:. The command uses the mysqldump command to dump the database to standard out, then sed is used to replace latin1 with utf8 in the dump, iconv is used to convert the dump from latin1 character encoding to utf8, and finally the mysql command is used to restore the resulting backup to the database server.
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Published at by John Collins. Introduction When you create a new database on MySQL, the default behaviour is to create a database supporting the latin1 character set. Creating a test database Firstly we are going to create a test database for testing the migration process.
John Collins I have been writing about web technology and software development since Adding a composite unique key to an existing MySQL table Finding the table containing a column name in MySQL This section describes issues that you may face when converting character data between the utf8mb3 and utf8mb4 character sets.
This discussion focuses primarily on converting between utf8mb3 and utf8mb4but similar principles apply to converting between the ucs2 character set and character sets such as utf16 or utf The utf8mb3 and utf8mb4 character sets differ as follows:.
This discussion refers to the utf8mb3 and utf8mb4 character set names to be explicit about referring to 3-byte and 4-byte UTF-8 character set data. The exception is that in table definitions, utf8 is used because MySQL converts instances of utf8mb3 specified in such definitions to utf8which is an alias for utf8mb3.
One advantage of converting from utf8mb3 to utf8mb4 is that this enables applications to use supplementary characters. One tradeoff is that this may increase data storage space requirements.
In terms of table content, conversion from utf8mb3 to utf8mb4 presents no problems:. For a BMP character, utf8mb4 and utf8mb3 have identical storage characteristics: same code values, same encoding, same length. For a supplementary character, utf8mb4 requires four bytes to store it, whereas utf8mb3 cannot store the character at all. When converting utf8mb3 columns to utf8mb4you need not worry about converting supplementary characters because there will be none. Consequently, to convert tables from utf8mb3 to utf8mb4it may be necessary to change some column or index definitions.
Suppose that a table has this definition:. The following statement converts t1 to use utf8mb4 :. The catch when converting from utf8mb3 to utf8mb4 is that the maximum length of a column or index key is unchanged in terms of bytes.
Therefore, it is smaller in terms of characters because the maximum length of a character is four bytes instead of three.
Convert an Entire MySQL Table to UTF-8
Check all definitions of utf8mb3 columns and make sure they will not exceed the maximum length for the storage engine. Check all indexes on utf8mb3 columns and make sure they will not exceed the maximum length for the storage engine. Sometimes the maximum can change due to storage engine enhancements. If the preceding conditions apply, you must either reduce the defined length of columns or indexes, or continue to use utf8mb3 rather than utf8mb4. You cannot convert it to utf8mb4 unless you also change the data type to a longer type such as TEXT.
If you currently have utf8mb3 columns with indexes longer than characters, you must index a smaller number of characters. To use utf8mb4 instead, the index must be smaller:. The preceding types of changes are most likely to be required only if you have very long columns or indexes.
As long as no 4-byte characters are sent from the server, there should be no problems.
Otherwise, applications that expect to receive a maximum of three bytes per character may have problems. Conversely, applications that expect to send 4-byte characters must ensure that the server understands them. For replication, if character sets that support supplementary characters are to be used on the master, all slaves must understand them as well. Also, keep in mind the general principle that if a table has different definitions on the master and slave, this can lead to unexpected results.
For example, the differences in maximum index key length make it risky to use utf8mb3 on the master and utf8mb4 on the slave.
If you have converted to utf8mb4utf16utf16leor utf32and then decide to convert back to utf8mb3 or ucs2 for example, to downgrade to an older version of MySQLthese considerations apply:.Cast functions and operators enable conversion of values from one data type to another.
For example, these are legal:. Normally, you cannot compare a BLOB value or other binary string in case-insensitive fashion because binary strings use the binary character set, which has no collation with the concept of lettercase. Comparisons of the resulting string use its collation. For example, if the conversion result character set has a case-insensitive collation, a LIKE operation is not case-sensitive.
To use a different character set, substitute its name for utf8mb4 in the preceding statements and similarly to use a different collation. For example, a comparison of these strings results in an error because they have different character sets:.
Converting one of the strings to a character set compatible with the other enables the comparison to occur without error:. For string literals, another way to specify the character set is to use a character set introducer. Unlike conversion functions such as CASTor CONVERTwhich convert a string from one character set to another, an introducer designates a string literal as having a particular character set, with no conversion involved.
Character set conversion is also useful preceding lettercase conversion of binary strings. To perform lettercase conversion of a binary string, first convert it to a nonbinary string using a character set appropriate for the data stored in the string:. The cast functions are useful for sorting ENUM columns in lexical order. Normally, sorting of ENUM columns occurs using the internal numeric values. Casting the values to CHAR results in a lexical sort:. For temporal values, there is little need to use CAST to extract data in different formats.
To cast a string to a number, you normally need do nothing other than use the string value in numeric context:. That is also true for hexadecimal and bit literals, which are binary strings by default:. A string used in an arithmetic operation is converted to a floating-point number during expression evaluation. MySQL supports arithmetic with both signed and unsigned bit values. If either operand is a floating-point value, the result is a floating-point value and is not affected by the preceding rule.
The BINARY operator converts the expression to a binary string a string that has the binary character set and binary collation. A common use for BINARY is to force a character string comparison to be done byte by byte using numeric byte values rather than character by character. To convert a string expression to a binary string, these constructs are equivalent:. For example, if the table default character set is utf8mb4these two column definitions are equivalent:.
For example, the following pairs of definitions are equivalent:.Web Development. Using a PHP script I made the conversion and it worked perfectly. Thank You so Much!! I have searched everywhere for a solution.
This is the only one that works!! Thank Goodness!! How long does it take to convert the database?Skate 3 ps3 best buy
I got the success message but when I tried to upload the db to the new server still getting the error. My database is very big, like M. You have to edit your php. I tried this script on my localhost installation and got a success message. What else do I need to do for a successful migration. I do not know any programming but can handle some code editing. Hope you can help. Email me your sql file at me sanjaybhowmick. Thanks for the offer. I have sent you the file. Still, it would be nice if you can please post the steps for doing it.
I will be needing it more than once and others might too. This site uses Akismet to reduce spam. Learn how your comment data is processed. August 12, 19 Comments. View the code on Gist. Database PHP. Previous Post Next Post. You may also like October 22, May 3,
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