why cast,convert donot work where round,floor works in the following case-CodePudding

I am a beginner to MySQL, i am trying to solve the following question

''' https://www.hackerrank.com/challenges/average-population/problem?isFullScreen=true&h_r=next-challenge&h_v=zen&h_r=next-challenge&h_v=zen '''

where I need to round the average of all cities population, coming from the normal c ,c background I thought casting a decimal to int would round the integer but it's showing the following error

''' ERROR 1064 (42000) at line 1: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'int) from city' at line 1 ''' for the following code

''' select cast(avg(population) as int) from city; ''' same error with convert as well. could you please why this doesn't work where cast(25.5 as int) works.

CodePudding user response：

When we use CAST or CONVERT function in mysql, the int is not a permitted type. Mysql has SIGNED [INTEGER] or UNSIGNED [INTEGER] for the same.

Reference: MySQL CAST function.

Tip: For rounding in MySQL you can also use Round function.