Why is SELECT * considered harmful? - Stack Overflow

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Answer by Developer_Suraj for Why is SELECT * considered harmful?

WHY YOU SHOULD NOT ALWAYS USE SELECT * FROM: Select * means you are retrieving all the records from that table with all columns but what if there are thousands, lakhs or more records? So it will take too much time we can say as a performance issue because it can take to much time if your table have lots of records. Simply it will lack your database...

Answer by Wing for Why is SELECT * considered harmful?

All the above answers are good, but if you reached this far and are still not convinced... Selecting the columns you need, makes queries almost self documenting. You get an idea what type of data the query will return, which you will never know with SELECT *. Nothing makes you look like newbie more than using SELECT * where it should't be. Just...

Answer by shaurya uppal for Why is SELECT * considered harmful?

REASONS WHY NOT TO USE SELECT * FROM TABLE:- Unnecessary I/O Increase Network traffic Fragile views Conflict in Join Queries More application memory Risky while copying data Depends on column order Always use column names will help you always in a large scale database.

Answer by lad2025 for Why is SELECT * considered harmful?

There is also more pragmatic reason: money. When you use cloud database and you have to pay for data processed there is no explanation to read data that you will immediately discard. For example: BigQuery: Query pricing Query pricing refers to the cost of running your SQL commands and user-defined functions. BigQuery charges for queries...

Answer by Aradhana Mohanty for Why is SELECT * considered harmful?

Selecting with column name raises the probability that database engine can access the data from indexes rather than querying the table data. SELECT * exposes your system to unexpected performance and functionality changes in the case when your database schema changes because you are going to get any new columns added to the table, even though, your...

Answer by kllee for Why is SELECT * considered harmful?

Understand your requirements prior to designing the schema (if possible). Learn about the data, 1)indexing 2)type of storage used, 3)vendor engine or features; ie...caching, in-memory capabilities 4)datatypes 5)size of table 6)frequency of query 7)related workloads if the resource is shared ...

Answer by Anvesh for Why is SELECT * considered harmful?

Reference taken from this article. Never go with "SELECT *", I have found only one reason to use "SELECT *" If you have special requirements and created dynamic environment when add or delete column automatically handle by application code. In this special case you don’t require to change application and database code and this will automatically...

Answer by Kelly S. French for Why is SELECT * considered harmful?

Think of it as reducing the coupling between the app and the database. To summarize the 'code smell' aspect:SELECT * creates a dynamic dependency between the app and the schema. Restricting its use is one way of making the dependency more defined, otherwise a change to the database has a greater likelihood of crashing your application.

Answer by supercat for Why is SELECT * considered harmful?

If you name the columns in a SELECT statement, they will be returned in the order specified, and may thus safely be referenced by numerical index. If you use "SELECT *", you may end up receiving the columns in arbitrary sequence, and thus can only safely use the columns by name. Unless you know in advance what you'll be wanting to do with any new...

Answer by OMG Ponies for Why is SELECT * considered harmful?

The asterisk character, "*", in the SELECT statement is shorthand for all the columns in the table(s) involved in the query. Performance The * shorthand can be slower because: Not all the fields are indexed, forcing a full table scan - less efficient What you save to send SELECT * over the wire risks a full table scan Returning more data...

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