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Fast way to discover the row count of a table in PostgreSQL
...in your case.
Instead of getting the exact count (slow with big tables):
SELECT count(*) AS exact_count FROM myschema.mytable;
You get a close estimate like this (extremely fast):
SELECT reltuples::bigint AS estimate FROM pg_class where relname='mytable';
How close the estimate is depends on ...
SQL query to find record with ID not in another table
...
Try this
SELECT ID, Name
FROM Table1
WHERE ID NOT IN (SELECT ID FROM Table2)
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MySQL select one column DISTINCT, with corresponding other columns
I want to select DISTINCT results from the FirstName column, but I need the corresponding ID and LastName .
12 Answe...
SELECT INTO using Oracle
I'm trying to do a SELECT INTO using Oracle. My query is:
3 Answers
3
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When to use SELECT … FOR UPDATE?
Please help me understand the use-case behind SELECT ... FOR UPDATE .
2 Answers
2
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PostgreSQL return result set as JSON array?
...
TL;DR
SELECT json_agg(t) FROM t
for a JSON array of objects, and
SELECT
json_build_object(
'a', json_agg(t.a),
'b', json_agg(t.b)
)
FROM t
for a JSON object of arrays.
List of objects
This section de...
How can I list ALL grants a user received?
...ust direct table grants (e.g., grants via roles, system privileges such as select any table, etc.), here are some additional queries:
System privileges for a user:
SELECT PRIVILEGE
FROM sys.dba_sys_privs
WHERE grantee = <theUser>
UNION
SELECT PRIVILEGE
FROM dba_role_privs rp JOIN role_...
1052: Column 'id' in field list is ambiguous
...and tbl_section which has both the id field in them. How do I go about selecting the id field, because I always get this error:
...
Which is fastest? SELECT SQL_CALC_FOUND_ROWS FROM `table`, or SELECT COUNT(*)
...irm this - I just updated a query with 4 joins on a 168,000 row database. Selecting just the first 100 rows with a SQL_CALC_FOUND_ROWS took over 20 seconds; using a separate COUNT(*) query took under 5 seconds (for both count + results queries).
– Sam Dufel
Ju...
How to select between brackets (or quotes or …) in Vim?
...Computed solution coefficients:
As CMS noted, this works for visual mode selection as well - just use vi), vi}, vi', etc.
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