![]() ![]() ![]() IF (EXISTS (SELECT * FROM INFORMATION_SCHEMA. IF (EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_SCHEMA = 'dbo' AND TABLE_NAME = 'TableB')) IF (EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_SCHEMA = 'dbo' AND TABLE_NAME = 'TableA')) Then select the records of the table variable, and you will have the rows of each existing table. PRINT sp_executesql 2: Use a table variable, insert only the rows of the tables that exist in your database. Note that status is whether the host is online or not. The following are the steps that help us to count the number of rows of all tables in a particular database: Step 1: First, we need to get all table names available in a database. SELECT = + 'Select id,name from ' + tablename + ' Union All ' From = - 9) Simple: I would like to count the number of rows from the sub-query. MySQL also allows us to get the number of rows of all tables in a specific database. WHEN IS NULL AND name = 'tableC' THEN 'select * from tableC' END This function returns 0 if it does not find any matching rows. Tom Cooper 8,441 Jan 13, 2022, 9:27 AM Sorry, I misread your question. It is a type of aggregate function whose return type is BIGINT. SELECT += CASE WHEN IS NOT NULL AND name = 'tableC' THEN ' union all select id,name from tableC' It allows us to count all rows or only some rows of the table that matches a specified condition. The database contains multiple tables, each with different sizes and varying numbers of rows. WHEN IS NULL AND name = 'tableB' THEN 'select * from tableB' END The Count is an aggregate function that returns a single concise result working on a table’s entire set of rows. SELECT += CASE WHEN IS NOT NULL AND name = 'tableB' THEN ' union all select id,name from tableB' SELECT = CASE WHEN name = 'tableA' THEN 'select id,name from tableA ' END More columns also required adding to the GROUP BY portion of the query.Solution 1: Dynamically modify the UNION statement based on whether the table exists.Ĭheck these two alternative methods: CREATE TABLE tableA(id INT,name VARCHAR(20))ĬREATE TABLE tableB(id INT,name VARCHAR(20))ĬREATE TABLE tableC(id INT,name VARCHAR(20)) I ran across this while trying to perform a similar task with a query containing about a dozen columns. This fetches all of the rows from the table. How to Resolve Column count doesn’t match value count at row 1 1 Comment / Last updated: JAre you getting the error Column count doesn’t match value count at row 1 in MySQL In this article, I’ll show you how to resolve this error, as well as what it means, and some examples. I do believe my approach is a bit easier to follow. We then create a variable named numberofrows, which we set equal to cursor.execute(SELECT FROM Tablename). The COUNT() function permits you to sum all rows or only rows matching the condition. That is still significantly slower then the other two queries. The COUNT() method returns the sum of rows residing in a specific table. Adding a key to the user_id on the posts and pages tables avoids the file sort and sped up the slow query to only take 18 seconds. Using EXPLAIN with each of the queries shows that both of your approaches involves a filesort which is avoided with my query. Your updated simpler method took over 2000 times as long (nearly 3 minutes compared to. Limited testing showed nearly identical performance with this query to your query using left join to select subqueries. To test performance differences, I loaded the tables with 16,000 posts and nearly 25,000 pages. (select count(*) from pages where er_id=er_id) as page_count (select count(*) from posts where er_id=er_id) as post_count, My solution involves the use of dependent subqueries. INSERT INTO users (name) VALUES ( 'Jen ') ĬREATE TABLE posts (post_id INT PRIMARY KEY AUTO_INCREMENT, user_id INT) ĬREATE TABLE pages (page_id INT PRIMARY KEY AUTO_INCREMENT, user_id INT) INSERT INTO users (name) VALUES ( 'Simon ') INSERT INTO users (name) VALUES ( 'Matt ') SELECT TABLESCHEMA AS Database, TABLENAME AS Table, ROUND((DATALENGTH + INDEXLENGTH) / 1024 / 1024) AS Size (MB) FROM informationschema.TABLES ORDER. CREATE TABLE users (user_id INT PRIMARY KEY AUTO_INCREMENT, name VARCHAR( 20))
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