I have a table called A where records contains some column name of table B.
table A
Id, columnName
1 col1
2 col2
3 col3
table B
ID, col1, col2, col3, col4, col5
I want to select columns of B based on the value of table A.
Example
Select col1, col2, col3
from B
If the record number 3 in table A were deleted the sql statement will be.
Select col1, col2
from B
You need a join. A basic SQL construct.
http://www.w3schools.com/sql/sql_join_inner.asp
Related
Lets say I have a table called TABLE with the columns col1, col2, col3 and col4
I want to select col1, col2 and col3 but distinct col2 values from the others, but I can't do it.
I tried something like this:
SELECT DISTINCT "col1", "col2", "col3" FROM [Table] WHERE col1 = Values
But the output brings me more than one record of col 2 with the same value.
I know that is because the distinct filtered all the columns that i specified, but i don't know how to get all the columns and filter only the values of col2.
Is it possible to SELECT more than 1 column but filter only one of them with SELECT DISTINCT ?
As you said, distinct just limits the full set of columns to eliminate duplicates. Instead, I'd just use an aggregate function with a GROUP BY statement.
SELECT MAX(col1) AS col1, col2,
MAX(col3) AS col3
FROM tbl
GROUP BY col2
That will take the top value alphanumerically from the supplied columns. Or, to list all values separated by commas:
SELECT STRING_AGG(col1,',') AS col1, col2,
STRING_AGG(col3,',') AS col3
FROM tbl
GROUP BY col2
I want to do something like this using BigQuery.
Input Table
Col1
Col2
Col3
Col4
1
A,B,C
123
789
Output Table
ID
COL
VALUE
1
COL1
1
1
COL2
A,B,C
1
COL3
123
1
COL4
789
I got this in hive with LATERAL VIEW explode(MAP), but I can't get the same in bigquery.
Consider below approach
select id, col, value
from (select *, row_number() over() as id from your_table)
unpivot (value for col in (Col1, Col2, Col3, Col4))
f apply to sample data in your question
with your_table as (
select '1' Col1, 'A,B,C' Col2, '123' Col3, '789' Col4
)
output is
Note - this particular approach requires all columns (Col1 - Col4) to be of the same type. If this is not a case you will need first apply cast for some of those to make them string
If it's a discrete number of columns, you can use UNIONs for this...
select id, 'Col1' as Column, col1 as Value
from table
union all
select id, 'Col2' as Column, col2 as Value
from table
union all
select id, 'Col3' as Column, col3 as Value
from table
I have 2 SQL's and the result come fine. They are no relation between those 2 queries but I want to see all the rows in single column.
e.g.
Select col1,col2,sum(col3) as col3 from table a
select col4,col5 from table b
I would like the result to be
col1 col2 col3 col4 col5
If there is no equivalent row for either table a or table b replace with zeroes.
Could some one help me with this. thanks.
Since, you didn't provided any information like table structure or data inside each tables. You can cross join both tables.
select t.col1,t.col2,t.col3,t1.col1,t1.col2 from tab1 t,tab2 t1;
SQLFiddle
In both select statements add column based on rownum or row_number() and then full join results using this column:
select nvl(col1, 0) col1, nvl(col2, 0) col2, nvl(col3, 0) col3,
nvl(col4, 0) col4, nvl(col5, 0) col5
from
(select rownum rn, col1, col2, col3 from (
select col1, col2, sum(col3) col3 from tableA group by col1, col2)) a
full join (select rownum rn, col4, col5 from tableB) b using (rn)
SQLFiddle demo
I guess a UNION could be a pragmatic solution since the 2 queries are not related. They are just 2 data sets that should be retrieved in one statement:
Select col1,col2,sum(col3) as col3 from table a
UNION
select col4,col5, to_number(null) col6 from table b
Be aware of col6 in the example. SQL insists on retrieving an equal set of columns in a UNION statement. It is a good practice to retrieve columns with exactly the same datatype. Since the sum(col3) will yield a number datatype column, col6 should too.
The outcome of col4 and col5 will be shown in col1 and col2.
i have two tables table1 and table2. Table1 has only 1 row of data and 7 column.
for ex.
col1 col2 col3 col4 col5 col6 col7 having data such as
(123 , abc , dfg, ed , " " , sc , fgh)
table2 has 6 column .
i want to join these two table table on such a way that finla output should have 1st row having data of
table1 and from 2nd row data of 2nd table.
NO commom column is there between this two table
plz tell me how to write query for this.
Do you really need them on 2 separate rows?
In that case, you can use the UNION as follows,
Select col1, col2, col3, col4, col5, col6, col7
from table1
UNION
Select col1, col2, col3, col4, col5, col6, ''
from table2
That should return the two records in two different rows, with a null column for the table2 since it consists of one column less that table1.
However, you have to ensure that the column types are similar in both tables for it to match!
In my table,some records have all column values are the same, except one. I need write a query to get those records. what's the best way to do it? the table is like this:
colA colB colC
a b c
a b d
a b e
What's the best way to get all records with all the columns? Thanks for everyone's help.
Assuming you know that column3 will always be different, to get the rows that have more than one value:
SELECT Col1, Col2
FROM Table t
GROUP BY Col1, Col2
HAVING COUNT(distinct col3) > 1
If you need all the values in the three columns, then you can join this back to the original table:
SELECT t.*
FROM table t join
(SELECT Col1, Col2
FROM Table t
GROUP BY Col1, Col2
HAVING COUNT(distinct col3) > 1
) cols
on t.col1 = cols.col1 and t.col2 = cols.col2
Just select those rows that have the different values:
SELECT col1, col2
FROM myTable
WHERE colWanted != knownValue
If this is not what you are looking for, please post examples of the data in the table and the wanted output.
How about something like
SELECT Col1, Col2
FROM Table
GROUP BY Col1, Col2
HAVING COUNT(*) = 1
This will give you Col1, Col2 that have unique data.
Assuming col3 has the difs
SELECT Col1, Col2
FROM Table
GROUP BY Col1, Col2
HAVING COUNT(*) > 1
OR TO SHOW ALL 3 COLS
SELECT Col1, Col2, Col3
FROM Table1
GROUP BY Col1, Col2, Col3
HAVING COUNT(Col3) > 1