I am new to MySQL. I have designed few tables with Char datatype. Now I want to change all the char datatype columns to Varchar with respective size mentioned in Char.
For example.
Existing - Phone Char(10)
Expected - Phone Varchar(10)
There are around 50 Plus tables. I know how to alter the datatype for each and every table and column but is there any better way to change the datatype in a single shot.
If you can't write a script to do the job, write a script that writes a script to do the job!
You want a bunch of ALTER TABLE statements:
SET SESSION group_concat_max_len = 1000000; -- Bumps the limit of 1028
SELECT GROUP_CONCAT(
CONCAT(
'ALTER TABLE `',
table_name,
'` MODIFY COLUMN `',
column_name,
'` VARCHAR(',
character_maximum_length,
')'
)
SEPARATOR ';\n') your_alter_statements
FROM information_schema.columns
WHERE table_schema = 'concrete'
AND data_type = 'char';
This'll result in:
ALTER TABLE `table1` MODIFY COLUMN `col1` VARCHAR(10);
ALTER TABLE `table1` MODIFY COLUMN `col2` VARCHAR(10);
ALTER TABLE `table2` MODIFY COLUMN `col1` VARCHAR(10);
ALTER TABLE `table3` MODIFY COLUMN `col1` VARCHAR(10);
ALTER TABLE `table3` MODIFY COLUMN `col2` VARCHAR(10);
Run that and you can go home early!
UPDATE: Stopped the truncation by adding group_concat_max_len
. Made the length dynamic based on the columns length.
MySQL only one liner solution:
SELECT 'ALTER TABLE ',TABLE_NAME, ' MODIFY COLUMN ',COLUMN_NAME, CONCAT(' VARCHAR(', CHARACTER_MAXIMUM_LENGTH, ');')
FROM INFORMATION_SCHEMA.COLUMNS where DATA_TYPE = 'char' AND TABLE_SCHEMA='concrete'
Above query will return all ALTER TABLE
statements, example shown below:
ALTER TABLE tablename1 MODIFY COLUMN col_name1 VARCHAR(17);
ALTER TABLE tablename2 MODIFY COLUMN col_name2 VARCHAR(17);
ALTER TABLE tablename3 MODIFY COLUMN col_name3 VARCHAR(60);
Copy the resulting rows and execute, so you can go home even more early.
Additionally, below is PHP/MySQL solution:
// Initialise Connection
define('DB_HOST', 'HOST_NAME_HERE');
define('DB_NAME', 'DB_NAME_HERE');
define('DB_USER_NAME', 'DB_USER_NAME_HERE');
define('DB_PASSWORD', 'DB_PASSWORD_HERE');
$pdo = new PDO('mysql:host=' . DB_HOST . ';dbname=' . DB_NAME, DB_USER_NAME, DB_PASSWORD, [
PDO::ATTR_PERSISTENT => false,
PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES utf8"
]);
// Get a list of CHAR columns
$sql = "SELECT TABLE_NAME, COLUMN_NAME, CHARACTER_MAXIMUM_LENGTH, IS_NULLABLE, COLUMN_DEFAULT
FROM INFORMATION_SCHEMA.COLUMNS where DATA_TYPE = 'char' AND TABLE_SCHEMA='" . DB_NAME . "'";
$stmt = $pdo->prepare($sql);
$stmt->execute();
$data = $stmt->fetchAll(PDO::FETCH_ASSOC);
// Change CHAR to VARCHAR
foreach ($data as $rec) {
$ddq = 'ALTER TABLE ' . $rec['TABLE_NAME'] . ' CHANGE ' . $rec['COLUMN_NAME'] . ' ' . $rec['COLUMN_NAME'] . ' VARCHAR(' .
$rec['CHARACTER_MAXIMUM_LENGTH'] . ') ' . ($rec['IS_NULLABLE'] == 'YES' ? 'NULL' : 'NOT NULL') . (isset($rec['COLUMN_DEFAULT']) ? " DEFAULT '{$rec['COLUMN_DEFAULT']}'" : '');
$pdo->query($ddq);
}
After analyzing the web, I got the answer and changed the datatype using this query.
select
concat('ALTER TABLE ', table_name,' MODIFY COLUMN ', column_name,' ', REPLACE (column_type, 'char', 'varchar'),';')
from information_schema.columns
where
data_type='char'
and table_schema='DBName';
If your field is PK ('id' smallint unsigned for example) and some other tables have constraints with foreign keys for this PK use this query.
note: for modern mysql servers remove ONLY_FULL_GROUP_BY from Variables -> sql mode, by default it contains:
ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION
Then insert and execute this query:
SET group_concat_max_len = 10000;
SET @database_name = "database1";
SET @table_name = "table1";
SET @change = "mediumint unsigned";
SELECT DISTINCT
`table_name`,
`column_name`,
`constraint_name`,
`referenced_table_name`,
`referenced_column_name`,
CONCAT(
GROUP_CONCAT('ALTER TABLE `',table_name,'` DROP FOREIGN KEY `',constraint_name, '`' SEPARATOR ';'),
';',
GROUP_CONCAT('ALTER TABLE `',table_name,'` CHANGE `',column_name,'` `',column_name,'` ',@change SEPARATOR ';'),
';',
CONCAT('ALTER TABLE `',@table_name,'` CHANGE `',referenced_column_name,'` `',referenced_column_name,'` ',@change, ' NOT NULL AUTO_INCREMENT'),
';',
GROUP_CONCAT('ALTER TABLE `',table_name,'` ADD CONSTRAINT `',constraint_name,'` FOREIGN KEY(',column_name,') REFERENCES ',referenced_table_name,'(',referenced_column_name,')' SEPARATOR ';'),
';'
) AS query
FROM `information_schema`.`key_column_usage`
WHERE `referenced_table_name` IS NOT NULL
AND `referenced_column_name` IS NOT NULL
AND `constraint_schema` = @database_name
AND `referenced_table_name` = @table_name
GROUP BY `referenced_table_name`;
note: check EXTRA OPTIONS to show full text for fields in result. Then copy and execute all generated queries. Restore ONLY_FULL_GROUP_BY in Variables.
Enjoy!
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.