MySQL查询在更新后以不同的顺序返回列

Question

One of my programs was using this query to get the details of a selected table's columns:

SELECT c.COLUMN_NAME as column_name,
       c.COLUMN_TYPE as column_type,
       c.CHARACTER_MAXIMUM_LENGTH as length,
       c.TABLE_NAME as table_name,
       c.COLUMN_COMMENT as column_comment,
       k.REFERENCED_TABLE_NAME as reference_table,
       k.REFERENCED_COLUMN_NAME as reference_column
FROM information_schema.COLUMNS as c
LEFT JOIN information_schema.KEY_COLUMN_USAGE as k
    ON (k.TABLE_SCHEMA=c.TABLE_SCHEMA
   AND k.TABLE_NAME=c.TABLE_NAME
   AND k.COLUMN_NAME=c.COLUMN_NAME
   AND k.POSITION_IN_UNIQUE_CONSTRAINT IS NOT NULL)
 WHERE c.TABLE_SCHEMA='$db_name'
   AND c.TABLE_NAME='$table_name'

The result used to be:

array(36) { [0]=> array(7) { ["column_name"]=> string(2) "id" ["column_type"]=> string(7) ...

The first column in that table is id , and in the results array, the first index was id (as it's supposed to be).

Now, however, after updating PHP (from 5.6 to 7.3) and MySQL, the results are sorting differently.

It is not sorting based on column's creation date priority and is instead sorting based on some unknown element ( id is 3rd index in array).

Is this a bug or something? How can I get the original sorting order back?

---

Okay, I just figured something out. MySQL is sorting the columns with a foreign keys first, and then the rest of the columns.

I don't want this! How can I get the original sort order back?

---

Here are my results. First is the current (wrong) output, then the expected output.

Incorrect output

column_name column_type length  table_name  column_comment  reference_table reference_column


qdqe_group  varchar(15)     15  md_report   name/Mach_Name  mach            Op_ID
owner       varchar(25)     25  md_report                   users           uName
Pile        varchar(12)     12  md_report                   depo            Depo_ID
Co_ID       varchar(3)       3  md_report   name/Co_NameF   contractors     Co_ID
Region_ID   varchar(2)       2  md_report   dependent/Mine_ID   regions     Region_ID
id          int(11)       NULL  md_report                   NULL            NULL
Submit_Date timestamp     NULL  md_report                   NULL            NULL
asd_ID      varchar(2)       2  md_report   input/multiple- NULL            Null
                                            asd-asd_ID,asd_
                                            nameF
wer_Report  date          NULL  md_report                   NULL            NULL
sdf_Qty     int(2)        NULL  md_report                   NULL            NULL
jyu_Time    time          NULL  md_report                   NULL            NULL
yuj_Work    float(6,2)    NULL  md_report                   NULL            NULL
Al2O3       float(4,2)    NULL  md_report                   NULL            NULL
SiO2        float(4,2)    NULL  md_report                   NULL            NULL
nh_Time     time          NULL  md_report                   NULL            NULL
ju_Work     float(6,2)    NULL  md_report                   NULL            NULL
we_Time     time          NULL  md_report                   NULL            NULL
xcv_Work    float(6,2)    NULL  md_report                   NULL            NULL
trh_Time    time          NULL  md_report                   NULL            NULL
ewr_Work    float(6,2)    NULL  md_report                   NULL            NULL
fgh_Time    time          NULL  md_report                   NULL            NULL
ert_Work    float(6,2)    NULL  md_report                   NULL            NULL
dfg_Time    time          NULL  md_report                   NULL            NULL
vf_Work     float(9,2)    NULL  md_report                   NULL            NULL
as_Time     time          NULL  md_report                   NULL            NULL

Here it is their real position in MySQL: (I changed some of the names for personal reasons)

Expected output

column_name column_type length  table_name  column_comment  reference_table reference_column


id          int(11)       NULL  md_report                   NULL            NULL
Submit_Date timestamp     NULL  md_report                   NULL            NULL
owner       varchar(25)     25  md_report                   users           uName
wer_Report  date          NULL  md_report                   NULL            NULL
Co_ID       varchar(3)       3  md_report   name/Co_NameF   contractors     Co_ID
Region_ID   varchar(2)       2  md_report   dependent/Mine_ID   regions     Region_ID
asd_ID      varchar(2)       2  md_report   input/multiple- NULL            NULL
                                            asd-asd_ID,asd_
                                            nameF
qdqe_group  varchar(15)     15  md_report   name/Mach_Name  mach            Op_ID
sdf_Qty     int(2)        NULL  md_report                   NULL            NULL
jyu_Time    time          NULL  md_report                   NULL            NULL
yuj_Work    float(6,2)    NULL  md_report                   NULL            NULL
Pile        varchar(12)     12  md_report                   depo            Depo_ID
Al2O3       float(4,2)    NULL  md_report                   NULL            NULL
SiO2        float(4,2)    NULL  md_report                   NULL            NULL
nh_Time     time          NULL  md_report                   NULL            NULL
ju_Work     float(6,2)    NULL  md_report                   NULL            NULL
we_Time     time          NULL  md_report                   NULL            NULL
xcv_Work    float(6,2)    NULL  md_report                   NULL            NULL
trh_Time    time          NULL  md_report                   NULL            NULL
ewr_Work    float(6,2)    NULL  md_report                   NULL            NULL
fgh_Time    time          NULL  md_report                   NULL            NULL
ert_Work    float(6,2)    NULL  md_report                   NULL            NULL
dfg_Time    time          NULL  md_report                   NULL            NULL
vf_Work     float(9,2)    NULL  md_report                   NULL            NULL
as_Time     time          NULL  md_report                   NULL            NULL

As you can see, MySQL sorted all the columns with references at the top of the results.

I want to get them in their real position with those details.

The new result is not logical anyway. I would really appreciate it if you could explain to me what is happening here.

Answer 1

There is no "default" sort order in a SQL table, at least none which is required by the ANSI standard (or, as you have seen here, implemented by MySQL). If you want your result set in a certain order, you should add a proper ORDER BY clause, eg

SELECT
    c.COLUMN_NAME as column_name,
    c.COLUMN_TYPE as column_type,
    ...
ORDER BY
    c.COLUMN_NAME;

As to why the perceived sort order has changed, it probably has to do with how the records are being fetched from the database. As the underlying data changes, the way MySQL will choose to access the records might also change.

Answer 2

I don't know why your output changed, but I think that to get the output you want, you can use an ORDER BY clause to order by the ordinal position.

ORDER BY c.ORDINAL_POSITION

When I ran your query on one of my own MySQL databases, I added a c.* to your list of SELECT ed columns. From all the extra columns displayed, the ORDINAL_POSITION seems like it might be what you are looking for.

So your final query might looks something like this:

SELECT c.COLUMN_NAME as column_name,
       c.COLUMN_TYPE as column_type,
       c.CHARACTER_MAXIMUM_LENGTH as length,
       c.TABLE_NAME as table_name,
       c.COLUMN_COMMENT as column_comment,
       k.REFERENCED_TABLE_NAME as reference_table,
       k.REFERENCED_COLUMN_NAME as reference_column
FROM information_schema.COLUMNS as c
LEFT JOIN information_schema.KEY_COLUMN_USAGE as k
    ON (k.TABLE_SCHEMA=c.TABLE_SCHEMA
      AND k.TABLE_NAME=c.TABLE_NAME
      AND k.COLUMN_NAME=c.COLUMN_NAME
      AND k.POSITION_IN_UNIQUE_CONSTRAINT IS NOT NULL)
WHERE c.TABLE_SCHEMA='$db_name'
      AND c.TABLE_NAME='$table_name'
ORDER BY c.ORDINAL_POSITION