mysql - mysql如何计算列数和行数

Question

我有一个要求，我需要计算给定数据库的列数、行数和每个表的大小。

下面的查询没有给出准确的结果，

SELECT t1.table_name, t1. table_rows,COUNT(t2.table_name) AS table_colums, t1. data_length 
FROM INFORMATION_SCHEMA.TABLES t1 
JOIN (SELECT table_name FROM INFORMATION_SCHEMA.COLUMNS WHERE table_schema='my_db_name') t2 
ON t1.table_name=t2.table_name 
WHERE t1.TABLE_SCHEMA = 'my_db_name';

有什么线索吗？

Answer 1

计算行数:

SELECT COUNT(*) FROM yourtable;

计数列:

SELECT count(*)
FROM information_schema.columns
WHERE table_name = 'yourtable'

如果您的意思是每个表的大小，即以 MB 为单位的大小，那么:

SELECT 
    table_name AS `Table`, 
    round(((data_length + index_length) / 1024 / 1024), 2) `Size in MB` 
FROM information_schema.TABLES 
WHERE table_schema = "yourdatabase"
    AND table_name = "yourtable";