如何在mysql表中获取列的大小

Question

我试图找出表格中一列的确切大小。 PHPMyAdmin不显示列的大小，只显示表的大小。

我能以任何方式获得列的大小吗？

三江源

Answer 1

如果您想从table = TABLE_NAME中找出column = COLUMN_NAME的大小，您可以随时运行如下查询：

SELECT sum(char_length(COLUMN_NAME)) 
FROM TABLE_NAME;

返回的大小以字节为单位。如果你想要它在kb，你可以把它除以1024，如下：

SELECT sum(char_length(COLUMN_NAME))/1024 
FROM TABLE_NAME;

Answer 2

SELECT column_name, 
       character_maximum_length 
FROM   information_schema.columns 
WHERE  table_schema = Database() 
       AND -- name of your database 
       table_name = 'turno' 
       AND -- name of your table 
       column_name = 'nombreTurno' -- name of the column 

• SQLFiddle Demo

INFORMATION_SCHEMA.COLUMNS

如果您想要整个表格大小，请使用此

SELECT table_name                                                 AS "Tables", 
       Round(( ( data_length + index_length ) / 1024 / 1024 ), 2) "Size in MB" 
FROM   information_schema.tables 
WHERE  table_schema = "$db_name" 
ORDER  BY ( data_length + index_length ) DESC; 

修改

SELECT column_name, 
       character_maximum_length 
FROM   information_schema.columns 
WHERE  table_schema = 'websi_db1' 
       AND table_name = 'thread' 
       AND column_name = 'title' 

Source

Answer 3

如果您是从脚本执行此操作，则可以在建立连接后运行此命令（因此已选择数据库）：

SELECT  character_maximum_length
FROM information_schema.columns
WHERE table_name = ? AND column_name = ?

分别用表名和列名替换？。