pgsql 
postgres=# \c my_db;
You are now connected to database "my_db" as user "postgres"
my_db=# create extension pgcrypto;
CREATE EXTENSION

如果報錯：
ERROR:  could not open extension control file "/home/postgres/postgresql-12.10/share/extension/pgcrypto.control": 沒有那個文件或目錄
解決辦法：
到安裝原文件目錄：
cd /home/postgres/software/postgresql-12.10/contrib/pgcrypt
[postgres@oracle pgcrypto] $ make USE-PGXS=1
 [postgres@oracle pgcrypto] $ make USE-PGXS=1 install
/bin/mkdir -p '/home/postgres/postgresql-12.10/lib'
/bin/mkdir -p '/home/postgres/postgresql-12.10/share/extension'
/bin/mkdir -p '/home/postgres/postgresql-12.10/share/extension'
/bin/install -c -m 755  pgcrypto.so '/home/postgres/postgresql-12.10/lib/pgcrypto.so'
/bin/install -c -m 644 ./pgcrypto.control '/home/postgres/postgresql-12.10/share/extension/'
/bin/install -c -m 644 ./pgcrypto--1.3.sql ./pgcrypto--1.2--1.3.sql ./pgcrypto--1.1--1.2.sql ./pgcrypto--1.0--1.1.sql ./pgcrypto--unpackaged--1.0.sql  '/home/postgres/postgresql-12.10/share/extension/'

加密方法：
select cast(encrypt('明文','mima','aes') as text)
==生成密文：\x0980edb56771107706c148fd6f902d2a

解密方法：
select convert_from(decrypt('密文','秘鑰','aes'),'SQL_ASCII');
select convert_from(decrypt('\x0980edb56771107706c148fd6f902d2a','mima','aes'),'SQL_ASCII');
==生成明文：明文