如何計算mysql中的行數

Question

我有一個要求，我需要計算給定數據庫的列數，行數和每個表的大小。

以下查詢未提供確切結果，

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';

有什么線索嗎？

Answer 1

計算行數：

SELECT COUNT(*) FROM yourtable;

計數列：

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

如果用每個表的大小表示以MB為單位的大小，則：

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";

Answer 2

這個查詢解決了我的問題。

SELECT t1.table_name, t1.table_rows, 
(SELECT COUNT(*) 
FROM INFORMATION_SCHEMA.COLUMNS
WHERE table_schema = 'my_db_name'
AND table_name = t1.table_name) AS colsm, 
t1.data_length
FROM INFORMATION_SCHEMA.TABLES t1
WHERE t1.TABLE_SCHEMA = 'my_db_name';

Answer 3

這可能會為您提供所需的結果

SELECT t1.table_name
,round(((data_length + index_length) / 1024 / 1024), 2) `Size in MB`
,(select count(*) from information_schema.columns c where c.table_schema = t1.table_schema and c.table_name = t1.table_name) as cols
,t1.table_rows as rows
FROM INFORMATION_SCHEMA.TABLES t1 
WHERE t1.table_schema = 'my_db_name'