The differences and reasons between MySQL with and without quotation marks when querying string types

Recently, I have been working on data , Problems encountered .

It is to query the daily trading data of a stock when querying the historical data of the stock , Because I didn't pay attention when running threads python Write sql Without single quotation marks . As shown in the figure below ：

And then run the task regularly on the lost server , The next morning, I found that the data didn't come out . And then the tragedy . Just find out why . Generally, the amount of data is small, and we can't see the difference between them . The following is the data volume of this table ：

I first print out the code with time , Time sharing printing . The log that comes out is as follows .

It can be seen from the figure that querying data takes a lot of time , And it takes almost no time to calculate . So I put select Copy the statement to navicat Run in , The following is the running time without single quotation marks ：

Then I run the stock code with single quotation marks . Here is a screenshot

It can be seen from the two pictures , There is a difference in query speed between the two 10 More than a second . It's built on 900W Measured on the basis of data . Therefore, you must pay attention to single quotation marks when querying string conditions .

Without single quotation marks mysql It will give you type conversion of the data in the database . This will take more time . See the following figure for the official documentation ：

On the blackboard ：1、 When querying by condition, query by character type , Do not cross character type queries across the Pacific .

              2、 For tables with a large amount of data, try to divide them , Index building .