Minor questions about COUNT in SQL.

select sum(case when columnname=1 then 1 else 0 end) as 'The number of 1',sum(case when columnname=0 then 1 else 0 end) as '0',cast(sum(case when columnname=1 then 1 else 0 end)/count(*)100 as varchar)+'%' as '1 percentage',cast(sum(case when columnname=0 then 1 else 0 end)/count(*)100 as varchar)+'%' as '0' from tablename

Table data item data

select count(*)count(*)/(select count(*)from table) from table group by data

Doesn't it work?? I haven't tried it.

select sum(zero) as zero,sum(one) as one,(sum(zero)+sum(one)) as he from(select (case when id=0 then count(*)else 0 end) as zero, (case when id=1 then count(*)else 0 end) as one from animal group by id)

This will find out 0, 1, and the sum. The rest is very simple, I believe you can handle it.

The number and the sum have been found, and the proportion is not a simple thing.

select sum(zero) as zero,sum(one) as one,(sum(zero)+sum(one)) as he ,sum(zero)/(sum(zero)+sum(one)) sum(one)/(sum(zero)+sum(one)) from(select (case when id=0 then count(*)else 0 end) as zero, (case when id=1 then count(*)else 0 end) as one from animal group by id)

Thus, the number of 0, the number of 1, the sum, the proportion of 0, the proportion of 1. It's all there, you pick.

Do you have to use a SQL statement?

I don't know if the method I use to declare variables is okay or not.

declare @count1 float,@count2 float

select @count1=count(*)from users where column=0

select @count2=count(*)from users where column=1

select @count1,cast(cast((@count1/count(*)100) as decimal(10,2)) as varchar)+'%',count2,cast(cast((@count2/count(*)100) as decimal(10,2)) as varchar)+'%'from table.

select sum(case when id=0 then 1 esle 0 end) as in the case of 0 numbers, sum(case when id= 1 then 1 esle 0 ) as in the case of 1 number, count(*)as all green numbers, sum(case when id=0 then 1 esle 0 end ) count(*)100 ||'%'As Percentage 0 sum(case when id= 1 then 1 esle 0 ) count(*).'%'Proportion 1 from biao

select sum(case column when 0 then 1 else 0 end) as count0,sum(case column when 1 then 1 else 0 end) as count1,sum(case column when 0 then 1 else 0 end) count(*)as rate0,sum(case column when 1 then 1 else 0 end) count(*)as rate1 from table.

The percentage format is not processed.

There is no difference between count and count in SQL statements. Indicates the number of rows that match the specified criteria.

SQL count() syntax:

1. The SQL Count(Column Name) function returns the number of values of the specified column (null is not counted), for example: select count(column name) from table name.

2. The SQL Count(*) function returns the number of records in the table, for example: select count(*)from table name.

3. The SQL Count(distinct column name) function returns the number of different values of the specified column, for example: select count(distinct column name) from table name.

There is no substantial difference in the usage of count(0) and count(1) from SQL statements.

The count function in an SQL statement is the number of records that are returned for a query.

count(expr), count(*) the number of values in a column (if you specify a column name as expr) or the number of rows in a table or the number of rows in a group (if you specify *) count(expr) ignores null values, but count(*) includes them in the count.

Any real number can be filled in the parentheses of the count function in the SQL statement, which can be used normally.

Real numbers are used in parentheses in the following count function

private sub form_load()= "provider=;persist security info=false;data source=jwl_dbf" 'count (spare parts**) as sj

select count( from jwl_jiec"

zsl =set = adodc3

end sub

The operation interface is as follows:

First, the meaning is different.

count(1) counts the number of all fields that meet the criteria including null values. count(0) will return the total number of all existing rows in **, including those with null values, while count(column name) will return the total number of all rows in ** except null (columns with default values are also counted), distinct column name, and the result will be the result after removing null values and duplicate data.

Second, the role is different.

The main thing is the data field corresponding to count(1).

If count(1) is a polyindex, id, then count(1) must be fast. But the difference is very small. This is because count(*) automatically optimizes which field to specify.

So there's no need to count(?).Using count(*) sql will help you with optimization.

Third, the results of use are different.

When abc is empty, the second is not counted in the count, and the first is unconditionally counted in the count, proportional to a column of data.

The field name is abcab

In the case of null, the first query has 3 entries, and the second query results 2 entries.

The difference is:

When abc is empty, the second is counted in the count and the first is unconditionally counted.

Proportional column of data.

The field name is abcab

nullIn this case, the first query is 3, and the result of the second query is 2, you can get a few pieces of data by yourself to test it, and you will know the result.

It makes no difference. count is the meaning of summarization. Inside is written the list name.

Summarize how many rows there are in this column. For example, if you write 0 or 1, you can think of it as select 1 from table and use 1 as the column name to summarize the number of rows.

count(1) or count(0) is faster and has a constant in the middle, so it makes no difference.

count(*) This is the slowest because it has to find out what the column name is represented by *.

Hello subject, from the statement point of view, there is nothing wrong with the use of the count statement, but from the error report, it should be that the subject uses the character type instead of the corresponding number type when the seller is building the table. This is because when executing a statement, there is a numerical comparison, i.e., a numeric type compared to a numeric type. So when the sale price is of type varchar, you think that 1000<=1000, but in fact it is like a crack"1000"< 1000, to give an inappropriate example, it is like comparing the height of 175 with the weight of 180 is the same, and it cannot be compared with the hidden change.

Therefore, the subject should first convert the type of the sale price field to a numeric type, such as int

When the subject converts the sale price type to a numeric type, he will find that the execution of the statement is fine, but the result is different from the expected, and the solution isRemove all three case whens with all else 0s.Explain why:

Let's take a look at the description of the count() function on the official website

The function of the count(x) function is to calculate the number of entries when x is a non-null value, and the subject is now writing so, the condition is true, the product name is displayed, and the non-slag closed is displayed as 0, and null is not equal to 0 or the product name, so the final result of the three counts is 8 (Each case when the entire table is traversed, and then a temporary table is obtained, and count() counts the number of non-null entries in the temporary table

low_price |

T-shirt |Punch |

Fork |Cutting board |

Ballpoint pen |After removing the else 0 part of case when, the part that meets the conditions is displayed as the product name, and the part that is not displayed is null by default, and then according to the characteristics of the count() function, you can get the correct result:

low_price |

T-shirt |Punch |

null |

null |

null |

Fork |Cutting board |

Ballpoint pen |The correct statement is shown in the figure below:

This question can be processed using sumif, see screenshot for details

I hope it can help the subject, welcome to ask.

There can't be plural counts in a select, this grammatical structure is wrong, you can write three counts into three tables, and then orange smile takes out the corresponding value!

The number of records calculated by the count function is related to the user's group category field. sql1：select count(*)from tablename ;Explanation: The above statement is to query the total number of pieces of the tablename.

sql2：select count(name) from tablename group by name;Explanation: