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Unconventional superconductivity is one of the many fascinating research areas of condensed matter physics. Understanding the superconducting pairing mechanism and its connection with other competing states remains unclear. This thesis investigates electronic transitions, charge, and spin fluctuations of various single-crystalline superconductors using a combination of x-ray absorption, x-ray emission, and resonant inelastic x-ray scattering techniques. Room temperature x-ray absorption, x-ray emission, and partial fluorescence yield measurements were carried out on LaPt₂Si₂ single crystal at the Si 2p and La 4d edges. Atomic-like transitions from La 4d to 4f are observed in x-ray absorption and x-ray emission measurements. The x-ray emission spectrum of LaPt₂Si₂ at the Si 2p edge is compared to the Si p and d local partial density of states. Resonant inelastic x-ray scattering measurements on YFe₂Ge₂ single crystal are also presented in this thesis. Magnon dispersion in YFe₂Ge₂ crystal along (h,0) and (h,h) directions are extracted from resonant inelastic x-ray scattering spectra and inelastic neutron scattering experiments. The magnon dispersion is fitted with the dispersion relation for a square lattice using the nearest and next-nearest neighbor exchange interaction. In YFe₂Ge₂, the ferromagnetic exchange interaction is higher than the antiferromagnetic interaction. High-resolution resonant inelastic x-ray scattering spectra were measured on La_1.675Eu_0.2Sr_0.125CuO₄ superconductor at various temperatures. Charge density fluctuations with shorter correlation lengths have been shown to exist above the structural transition up to 200 K in La_1.675Eu_0.2Sr_0.125CuO₄. Phonon dispersion relation has also been mapped from high-resolution resonant inelastic x-ray scattering spectra. Softening of optical phonon mode in La_1.675Eu_0.2Sr_0.125CuO₄ is observed at low and high temperatures coinciding with the charge density wave vector.