Consultas SELECTCondiciones WHEREORDER BYFunciones de agregaciónJOINsINSERTUPDATEDELETEGestión de tablasRestriccionesSubconsultasFunciones de cadena/fecha
#Consultas SELECT
| Comando | Descripción | |
|---|---|---|
SELECT * FROM table | Seleccionar todas las columnas | |
SELECT col1, col2 FROM table | Seleccionar columnas específicas | |
SELECT DISTINCT col FROM table | Seleccionar valores distintos | |
SELECT col AS alias FROM table | Alias de columna | |
SELECT * FROM table LIMIT 10 | Limitar resultados | |
SELECT * FROM table OFFSET 5 | Omitir resultados |
#Condiciones WHERE
| Comando | Descripción | |
|---|---|---|
WHERE col = value | Igual a | |
WHERE col <> value | No igual a | |
WHERE col > value | Mayor que | |
WHERE col >= value | Mayor o igual que | |
WHERE col < value | Menor que | |
WHERE col <= value | Menor o igual que | |
WHERE col BETWEEN a AND b | Entre rango | |
WHERE col IN (v1, v2, v3) | En lista | |
WHERE col LIKE '%pattern%' | Coincidencia de patrón | |
WHERE col IS NULL | Verificar NULL | |
WHERE col IS NOT NULL | Verificar NOT NULL | |
WHERE cond1 AND cond2 | Condición AND | |
WHERE cond1 OR cond2 | Condición OR | |
WHERE NOT condition | Condición NOT |
#ORDER BY
| Comando | Descripción | |
|---|---|---|
ORDER BY col | Orden ascendente | |
ORDER BY col ASC | Ascendente (explícito) | |
ORDER BY col DESC | Orden descendente | |
ORDER BY col1, col2 | Múltiples columnas | |
ORDER BY col NULLS FIRST | NULLs primero | |
ORDER BY col NULLS LAST | NULLs último |
#Funciones de agregación
| Comando | Descripción | |
|---|---|---|
COUNT(*) | Contar filas | |
COUNT(col) | Contar no nulos | |
COUNT(DISTINCT col) | Contar distintos | |
SUM(col) | Suma | |
AVG(col) | Promedio | |
MIN(col) | Mínimo | |
MAX(col) | Máximo | |
GROUP BY col | Agrupar por | |
HAVING condition | Filtro de grupo |
#JOINs
| Comando | Descripción | |
|---|---|---|
INNER JOIN t2 ON t1.col = t2.col | Unión interna | |
LEFT JOIN t2 ON t1.col = t2.col | Unión izquierda | |
RIGHT JOIN t2 ON t1.col = t2.col | Unión derecha | |
FULL OUTER JOIN t2 ON ... | Unión externa completa | |
CROSS JOIN t2 | Producto cartesiano | |
SELF JOIN (t AS a, t AS b) | Auto unión | |
NATURAL JOIN t2 | Unión natural |
#INSERT
| Comando | Descripción | |
|---|---|---|
INSERT INTO t (cols) VALUES (vals) | Insertar una fila | |
INSERT INTO t VALUES (v1), (v2) | Insertar múltiples filas | |
INSERT INTO t SELECT ... | Insertar desde select | |
INSERT INTO t DEFAULT VALUES | Insertar valores por defecto |
#UPDATE
| Comando | Descripción | |
|---|---|---|
UPDATE t SET col = val | Actualizar todas las filas | |
UPDATE t SET col = val WHERE ... | Actualización condicional | |
UPDATE t SET c1 = v1, c2 = v2 | Actualizar múltiples columnas | |
UPDATE t SET col = col + 1 | Incrementar valor |
#DELETE
| Comando | Descripción | |
|---|---|---|
DELETE FROM t | Eliminar todas las filas | |
DELETE FROM t WHERE ... | Eliminación condicional | |
TRUNCATE TABLE t | Truncar tabla (rápido) |
#Gestión de tablas
| Comando | Descripción | |
|---|---|---|
CREATE TABLE t (col type, ...) | Crear tabla | |
DROP TABLE t | Eliminar tabla | |
ALTER TABLE t ADD col type | Agregar columna | |
ALTER TABLE t DROP COLUMN col | Eliminar columna | |
ALTER TABLE t RENAME TO new | Renombrar tabla | |
CREATE INDEX idx ON t(col) | Crear índice | |
DROP INDEX idx | Eliminar índice |
#Restricciones
| Comando | Descripción | |
|---|---|---|
PRIMARY KEY | Clave primaria | |
FOREIGN KEY REFERENCES t(col) | Clave foránea | |
UNIQUE | Restricción única | |
NOT NULL | No nulo | |
DEFAULT value | Valor por defecto | |
CHECK (condition) | Restricción de verificación | |
AUTO_INCREMENT / SERIAL | Auto incremento |
#Subconsultas
| Comando | Descripción | |
|---|---|---|
WHERE col IN (SELECT ...) | Subconsulta IN | |
WHERE col = (SELECT ...) | Subconsulta escalar | |
WHERE EXISTS (SELECT ...) | Subconsulta EXISTS | |
SELECT (SELECT ...) AS col | Subconsulta en SELECT | |
FROM (SELECT ...) AS t | Subconsulta en FROM | |
WITH cte AS (SELECT ...) | Expresión de tabla común |
#Funciones de cadena/fecha
| Comando | Descripción | |
|---|---|---|
CONCAT(s1, s2) | Concatenar cadenas | |
UPPER(str) / LOWER(str) | Mayúsculas/minúsculas | |
LENGTH(str) | Longitud de cadena | |
SUBSTRING(str, start, len) | Subcadena | |
TRIM(str) | Eliminar espacios | |
REPLACE(str, from, to) | Reemplazar cadena | |
NOW() / CURRENT_TIMESTAMP | Marca de tiempo actual | |
DATE(datetime) | Extraer fecha | |
YEAR(date) / MONTH(date) | Extraer año/mes | |
DATEDIFF(d1, d2) | Diferencia de fechas |
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