Merge 5615da920f into 1fd64e478a

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
 For a steady stream of TILs, [sign up for my newsletter](https://crafty-builder-6996.ck.page/e169c61186).
 
-_1580 TILs and counting..._
+_1581 TILs and counting..._
 
 See some of the other learning resources I work on:
 - [Ruby Operator Lookup](https://www.visualmode.dev/ruby-operators)
@@ -195,7 +195,7 @@ See some of the other learning resources I work on:
 - [Aliasing An Ansible Host](devops/aliasing-an-ansible-host.md)
 - [Allow Cross-Origin Requests To Include Cookies](devops/allow-cross-origin-requests-to-include-cookies.md)
 - [Allow HTTPS Through Your UFW Firewall](devops/allow-https-through-your-ufw-firewall.md)
-- [Check For Cached Site Assocation File For iOS](devops/check-for-cached-site-association-file-for-ios.md)
+- [Check For Cached Site Association File For iOS](devops/check-for-cached-site-association-file-for-ios.md)
 - [Check The Status of All Services](devops/check-the-status-of-all-services.md)
 - [Check The Syntax Of nginx Files](devops/check-the-syntax-of-nginx-files.md)
 - [Connect To An RDS PostgreSQL Database](devops/connect-to-an-rds-postgresql-database.md)
@@ -767,7 +767,7 @@ See some of the other learning resources I work on:
 - [Check If Clusters Are Upgrade Compatible](postgres/check-if-clusters-are-upgrade-compatible.md)
 - [Check If The Local Server Is Running](postgres/check-if-the-local-server-is-running.md)
 - [Check If User Role Exists For Database](postgres/check-if-user-role-exists-for-database.md)
-- [Check Table For Any Oprhaned Records](postgres/check-table-for-any-orphaned-records.md)
+- [Check Table For Any Orphaned Records](postgres/check-table-for-any-orphaned-records.md)
 - [Checking Inequality](postgres/checking-inequality.md)
 - [Checking The Type Of A Value](postgres/checking-the-type-of-a-value.md)
 - [Clear The Screen In psql](postgres/clear-the-screen-in-psql.md)
@@ -899,6 +899,7 @@ See some of the other learning resources I work on:
 - [Timestamp Functions](postgres/timestamp-functions.md)
 - [Toggling The Pager In PSQL](postgres/toggling-the-pager-in-psql.md)
 - [Track psql History Separately Per Database](postgres/track-psql-history-separately-per-database.md)
+- [Trim Leading And Trailing Space From String](postgres/trim-leading-and-trailing-space-from-string.md)
 - [Truncate All Rows](postgres/truncate-all-rows.md)
 - [Truncate Tables With Dependents](postgres/truncate-tables-with-dependents.md)
 - [Turning Timing On](postgres/turn-timing-on.md)

postgres/trim-leading-and-trailing-space-from-string.md

@@ -0,0 +1,58 @@
+# Trim Leading And Trailing Space From String
+
+PostgreSQL has a bunch of [string
+functions](https://www.postgresql.org/docs/current/functions-string.html),
+including several for doing various string trimming.
+
+We can use the simplest form of `trim` to remove leading and trailing space
+characters from a string.
+
+```sql
+> select trim('  Taco Cat ');
++----------+
+| btrim    |
+|----------|
+| Taco Cat |
++----------+
+```
+
+The syntax for calling `trim` is a bit odd relative to other PostgreSQL
+functions and functions in other languages. Here is the "grammar" as described
+in the docs:
+
+```
+trim ( [ LEADING | TRAILING | BOTH ] [ characters text ] FROM string text ) → text
+```
+
+We pick `leading`, `trailing`, or `both`, with `both` being the default. Then
+we specify the character(s) we want to remove. This is also optional, the
+default being the space character. Then we say `from` what string we want to
+trim those characters.
+
+Here we remove all sequential spaces from `both` ends of the given string:
+
+```sql
+> select trim(both from '  Taco Cat ');
++----------+
+| btrim    |
+|----------|
+| Taco Cat |
++----------+
+```
+
+To further demonstrate how `trim` works, here we remove all sequences made up
+of any of spaces, uppercase `T`, and lowercase `t` from `both` ends of the
+string:
+
+```sql
+> select trim(both ' Tt' from '  Taco Cat ');
++--------+
+| btrim  |
+|--------|
+| aco Ca |
++--------+
+```
+
+Notice that in all the above examples the column name of the result is `btrim`.
+That's probably because `btrim` (_trim both ends_) is being called under the
+hood for the `both` option.