Current date
Describe
Explain plans
Get type of expression
Run scripts
Show all tables
Show parameters
Truncate table
Run AWRs for Oracle

Current Date

MySQL

SELECT CURDATE();

SELECT NOW();

Postgres

SELECT CURRENT_DATE;

SELECT CURRENT_TIMESTAMP;

Oracle

SELECT SYSDATE FROM DUAL;

SELECT SYSTIMESTAMP FROM DUAL;

SQL Server

SELECT SYSDATETIME();

SELECT CURRENT_TIMESTAMP;

Db2

VALUES(CURRENT DATE);

VALUES(CURRENT TIMESTAMP);

SELECT CURRENT DATE FROM sysibm.sysdummy1;

SELECT CURRENT TIMESTAMP FROM sysibm.sysdummy1;

Describe

MySQL | Oracle

DESCRIBE <table_name>;

Postgres

\d <table_name>;

SQL Server

sp_help <table_name>;

Db2

DESCRIBE TABLE <table_name>;
DESCRIBE SELECT * FROM <table_name>;

Explain plans

MySQL

EXPLAIN [FORMAT = [TRADITIONAL | TREE | JSON]] <SQL>;

EXPLAIN ANALYZE <SQL>;

Postgres

EXPLAIN [ ANALYZE ] [ VERBOSE ] <SQL>;

Oracle

EXPLAIN PLAN FOR <SQL>;

SELECT *
FROM TABLE(DBMS_XPLAN.DISPLAY (FORMAT=>'ALL +OUTLINE'));

SQL Server

SET SHOWPLAN_TEXT ON;
<SQL>
<SQL>
<SQL>
SET SHOWPLAN_TEXT OFF;

Db2

CALL SYSPROC.SYSINSTALLOBJECTS('EXPLAIN', 'C', 
        CAST (NULL AS VARCHAR(128)), CAST (NULL AS VARCHAR(128)))

EXPLAIN PLAN FOR <SQL>;

db2exfmt -d <DB> -o explain.txt

Snowflake

EXPLAIN USING TABULAR <SQL>;

Get type of expression

Postgres

SELECT pg_typeof(<expression>);

Oracle

SELECT dump(<expression>) FROM DUAL;

Run scripts

MySQL

source <script path/file>

Postgres

\i <script path/file>

Oracle

@<script path/file>

SQL Server

:r <script path/file>

Db2

db2 -tvmf <script path/file>

Show all tables

MySQL

SHOW TABLES;

Postgres

\dt

SELECT * FROM pg_catalog.pg_tables;

Oracle

SELECT * FROM DBA_TABLES;

SQL Server

Db2

Snowflake

Show parameters

MySQL

SHOW VARIABLES [LIKE '<string>'];

Postgres

SHOW [<parameter> | ALL];

Oracle

SHOW PARAMETER <string>

Truncate table

MySQL | Oracle | SQL Server

TRUNCATE TABLE <table_name>;

Db2

TRUNCATE TABLE <table_name> IMMEDIATE;

Run AWRs for Oracle

# Little script to take an AWR snapshot and return the snap id
take_snapshot() {
  sql -s / as sysdba <<EOF
    set pagesize 0 feedback off verify off heading off echo off;
    select DBMS_WORKLOAD_REPOSITORY.CREATE_SNAPSHOT('ALL') AS a from dual;
    exit;
EOF
}

# Little script to get the dbid
get_dbid() {
  sql -s / as sysdba <<EOF
    set pagesize 0 feedback off verify off heading off echo off;
    select dbid from v\$database;
    exit;
EOF
}

# Generate AWR report (dbid, snap_id_begin, snap_id_end, log_file)
generate_snapshot() {
  sql -s / as sysdba > $4 <<EOF
    set pagesize 0 feedback off termout off;
    SELECT * FROM TABLE(DBMS_WORKLOAD_REPOSITORY.AWR_REPORT_HTML($1, 1, $2, $3));
    exit;
EOF
}

# Take snapshot ids
snap_id_begin=$(take_snapshot)
snap_id_end=$(take_snapshot)

dbid=$(get_dbid)
generate_snapshot($dbid, $snap_id_begin, $snap_id_end, "awr.html")