如何计算表中具有相同列值的行数? [英] How do you count the number of rows in a table that have the same value in value in a column?

问题描述

假设我有以下简单表格:

Suppose I have the following simple table:

create table mytable (
    desid bigint not null,
    ancid bigint not null
  );

insert into mytable (ancid,desid) values (1,10);
insert into mytable (ancid,desid) values (1,20);
insert into mytable (ancid,desid) values (1,21);
insert into mytable (ancid,desid) values (1,22);
insert into mytable (ancid,desid) values (2,30);
insert into mytable (ancid,desid) values (3,40);
insert into mytable (ancid,desid) values (3,41);
insert into mytable (ancid,desid) values (3,42);
insert into mytable (ancid,desid) values (3,43);

什么是SQL命令，它将输出以下信息:

What is the SQL command that will print out the following information:

4 rows with ancid=1
1 rows with ancid=2
4 rows with ancid=3

推荐答案

您可以通过按 ancid 进行分组来获取信息:

You can get the information by grouping by the ancid:

SELECT   ancid, COUNT(*)
FROM     mytable
GROUP BY ancid

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